The Dates
module provides two types for working with dates: Date
and DateTime
, representing day and millisecond precision, respectively; both are subtypes of the abstract TimeType
. The motivation for distinct types is simple: some operations are much simpler, both in terms of code and mental reasoning, when the complexities of greater precision don't have to be dealt with. For example, since the Date
type only resolves to the precision of a single date (i.e. no hours, minutes, or seconds), normal considerations for time zones, daylight savings/summer time, and leap seconds are unnecessary and avoided.
Both Date
and DateTime
are basically immutable Int64
wrappers. The single instant
field of either type is actually a UTInstant{P}
type, which represents a continuously increasing machine timeline based on the UT second [1]. The DateTime
type is not aware of time zones (naive, in Python parlance), analogous to a LocalDateTime in Java 8. Additional time zone functionality can be added through the TimeZones.jl package, which compiles the IANA time zone database. Both Date
and DateTime
are based on the ISO 8601 standard, which follows the proleptic Gregorian calendar. One note is that the ISO 8601 standard is particular about BC/BCE dates. In general, the last day of the BC/BCE era, 11231 BC/BCE, was followed by 111 AD/CE, thus no year zero exists. The ISO standard, however, states that 1 BC/BCE is year zero, so 00001231
is the day before 00010101
, and year 0001
(yes, negative one for the year) is 2 BC/BCE, year 0002
is 3 BC/BCE, etc.
The notion of the UT second is actually quite fundamental. There are basically two different notions of time generally accepted, one based on the physical rotation of the earth (one full rotation = 1 day), the other based on the SI second (a fixed, constant value). These are radically different! Think about it, a "UT second", as defined relative to the rotation of the earth, may have a different absolute length depending on the day! Anyway, the fact that Date
and DateTime
are based on UT seconds is a simplifying, yet honest assumption so that things like leap seconds and all their complexity can be avoided. This basis of time is formally called UT or UT1. Basing types on the UT second basically means that every minute has 60 seconds and every day has 24 hours and leads to more natural calculations when working with calendar dates.
Date
and DateTime
types can be constructed by integer or Period
types, by parsing, or through adjusters (more on those later):
julia> DateTime(2013) 20130101T00:00:00 julia> DateTime(2013,7) 20130701T00:00:00 julia> DateTime(2013,7,1) 20130701T00:00:00 julia> DateTime(2013,7,1,12) 20130701T12:00:00 julia> DateTime(2013,7,1,12,30) 20130701T12:30:00 julia> DateTime(2013,7,1,12,30,59) 20130701T12:30:59 julia> DateTime(2013,7,1,12,30,59,1) 20130701T12:30:59.001 julia> Date(2013) 20130101 julia> Date(2013,7) 20130701 julia> Date(2013,7,1) 20130701 julia> Date(Dates.Year(2013),Dates.Month(7),Dates.Day(1)) 20130701 julia> Date(Dates.Month(7),Dates.Year(2013)) 20130701
Date
or DateTime
parsing is accomplished by the use of format strings. Format strings work by the notion of defining delimited or fixedwidth "slots" that contain a period to parse and passing the text to parse and format string to a Date
or DateTime
constructor, of the form Date("20150101","ymd")
or DateTime("20150101","yyyymmdd")
.
Delimited slots are marked by specifying the delimiter the parser should expect between two subsequent periods; so "ymd"
lets the parser know that between the first and second slots in a date string like "20140716"
, it should find the 
character. The y
, m
, and d
characters let the parser know which periods to parse in each slot.
Fixedwidth slots are specified by repeating the period character the number of times corresponding to the width with no delimiter between characters. So "yyyymmdd"
would correspond to a date string like "20140716"
. The parser distinguishes a fixedwidth slot by the absence of a delimiter, noting the transition "yyyymm"
from one period character to the next.
Support for textform month parsing is also supported through the u
and U
characters, for abbreviated and fulllength month names, respectively. By default, only English month names are supported, so u
corresponds to "Jan", "Feb", "Mar", etc. And U
corresponds to "January", "February", "March", etc. Similar to other name=>value mapping functions dayname
and monthname
, custom locales can be loaded by passing in the locale=>Dict{String,Int}
mapping to the MONTHTOVALUEABBR
and MONTHTOVALUE
dicts for abbreviated and fullname month names, respectively.
One note on parsing performance: using the Date(date_string,format_string)
function is fine if only called a few times. If there are many similarly formatted date strings to parse however, it is much more efficient to first create a Dates.DateFormat
, and pass it instead of a raw format string.
julia> df = DateFormat("ymd"); julia> dt = Date("20150101",df) 20150101 julia> dt2 = Date("20150102",df) 20150102
You can also use the dateformat""
string macro. This macro creates the DateFormat
object once when the macro is expanded and uses the same DateFormat
object even if a code snippet is run multiple times.
julia> for i = 1:10^5 Date("20150101", dateformat"ymd") end
A full suite of parsing and formatting tests and examples is available in stdlib/Dates/test/io.jl
.
Finding the length of time between two Date
or DateTime
is straightforward given their underlying representation as UTInstant{Day}
and UTInstant{Millisecond}
, respectively. The difference between Date
is returned in the number of Day
, and DateTime
in the number of Millisecond
. Similarly, comparing TimeType
is a simple matter of comparing the underlying machine instants (which in turn compares the internal Int64
values).
julia> dt = Date(2012,2,29) 20120229 julia> dt2 = Date(2000,2,1) 20000201 julia> dump(dt) Date instant: Dates.UTInstant{Day} periods: Day value: Int64 734562 julia> dump(dt2) Date instant: Dates.UTInstant{Day} periods: Day value: Int64 730151 julia> dt > dt2 true julia> dt != dt2 true julia> dt + dt2 ERROR: MethodError: no method matching +(::Date, ::Date) [...] julia> dt * dt2 ERROR: MethodError: no method matching *(::Date, ::Date) [...] julia> dt / dt2 ERROR: MethodError: no method matching /(::Date, ::Date) julia> dt  dt2 4411 days julia> dt2  dt 4411 days julia> dt = DateTime(2012,2,29) 20120229T00:00:00 julia> dt2 = DateTime(2000,2,1) 20000201T00:00:00 julia> dt  dt2 381110400000 milliseconds
Because the Date
and DateTime
types are stored as single Int64
values, date parts or fields can be retrieved through accessor functions. The lowercase accessors return the field as an integer:
julia> t = Date(2014, 1, 31) 20140131 julia> Dates.year(t) 2014 julia> Dates.month(t) 1 julia> Dates.week(t) 5 julia> Dates.day(t) 31
While propercase return the same value in the corresponding Period
type:
julia> Dates.Year(t) 2014 years julia> Dates.Day(t) 31 days
Compound methods are provided, as they provide a measure of efficiency if multiple fields are needed at the same time:
julia> Dates.yearmonth(t) (2014, 1) julia> Dates.monthday(t) (1, 31) julia> Dates.yearmonthday(t) (2014, 1, 31)
One may also access the underlying UTInstant
or integer value:
julia> dump(t) Date instant: Dates.UTInstant{Day} periods: Day value: Int64 735264 julia> t.instant Dates.UTInstant{Day}(735264 days) julia> Dates.value(t) 735264
Query functions provide calendrical information about a TimeType
. They include information about the day of the week:
julia> t = Date(2014, 1, 31) 20140131 julia> Dates.dayofweek(t) 5 julia> Dates.dayname(t) "Friday" julia> Dates.dayofweekofmonth(t) # 5th Friday of January 5
Month of the year:
julia> Dates.monthname(t) "January" julia> Dates.daysinmonth(t) 31
As well as information about the TimeType
's year and quarter:
julia> Dates.isleapyear(t) false julia> Dates.dayofyear(t) 31 julia> Dates.quarterofyear(t) 1 julia> Dates.dayofquarter(t) 31
The dayname
and monthname
methods can also take an optional locale
keyword that can be used to return the name of the day or month of the year for other languages/locales. There are also versions of these functions returning the abbreviated names, namely dayabbr
and monthabbr
. First the mapping is loaded into the LOCALES
variable:
julia> french_months = ["janvier", "février", "mars", "avril", "mai", "juin", "juillet", "août", "septembre", "octobre", "novembre", "décembre"]; julia> french_monts_abbrev = ["janv","févr","mars","avril","mai","juin", "juil","août","sept","oct","nov","déc"]; julia> french_days = ["lundi","mardi","mercredi","jeudi","vendredi","samedi","dimanche"]; julia> Dates.LOCALES["french"] = Dates.DateLocale(french_months, french_monts_abbrev, french_days, [""]);
The above mentioned functions can then be used to perform the queries:
julia> Dates.dayname(t;locale="french") "vendredi" julia> Dates.monthname(t;locale="french") "janvier" julia> Dates.monthabbr(t;locale="french") "janv"
Since the abbreviated versions of the days are not loaded, trying to use the function dayabbr
will error.
julia> Dates.dayabbr(t;locale="french") ERROR: BoundsError: attempt to access 1element Array{String,1} at index [5] Stacktrace: [...]
It's good practice when using any language/date framework to be familiar with how dateperiod arithmetic is handled as there are some tricky issues to deal with (though much less so for dayprecision types).
The Dates
module approach tries to follow the simple principle of trying to change as little as possible when doing Period
arithmetic. This approach is also often known as calendrical arithmetic or what you would probably guess if someone were to ask you the same calculation in a conversation. Why all the fuss about this? Let's take a classic example: add 1 month to January 31st, 2014. What's the answer? Javascript will say March 3 (assumes 31 days). PHP says March 2 (assumes 30 days). The fact is, there is no right answer. In the Dates
module, it gives the result of February 28th. How does it figure that out? I like to think of the classic 777 gambling game in casinos.
Now just imagine that instead of 777, the slots are YearMonthDay, or in our example, 20140131. When you ask to add 1 month to this date, the month slot is incremented, so now we have 20140231. Then the day number is checked if it is greater than the last valid day of the new month; if it is (as in the case above), the day number is adjusted down to the last valid day (28). What are the ramifications with this approach? Go ahead and add another month to our date, 20140228 + Month(1) == 20140328
. What? Were you expecting the last day of March? Nope, sorry, remember the 777 slots. As few slots as possible are going to change, so we first increment the month slot by 1, 20140328, and boom, we're done because that's a valid date. On the other hand, if we were to add 2 months to our original date, 20140131, then we end up with 20140331, as expected. The other ramification of this approach is a loss in associativity when a specific ordering is forced (i.e. adding things in different orders results in different outcomes). For example:
julia> (Date(2014,1,29)+Dates.Day(1)) + Dates.Month(1) 20140228 julia> (Date(2014,1,29)+Dates.Month(1)) + Dates.Day(1) 20140301
What's going on there? In the first line, we're adding 1 day to January 29th, which results in 20140130; then we add 1 month, so we get 20140230, which then adjusts down to 20140228. In the second example, we add 1 month first, where we get 20140229, which adjusts down to 20140228, and then add 1 day, which results in 20140301. One design principle that helps in this case is that, in the presence of multiple Periods, the operations will be ordered by the Periods' types, not their value or positional order; this means Year
will always be added first, then Month
, then Week
, etc. Hence the following does result in associativity and Just Works:
julia> Date(2014,1,29) + Dates.Day(1) + Dates.Month(1) 20140301 julia> Date(2014,1,29) + Dates.Month(1) + Dates.Day(1) 20140301
Tricky? Perhaps. What is an innocent Dates
user to do? The bottom line is to be aware that explicitly forcing a certain associativity, when dealing with months, may lead to some unexpected results, but otherwise, everything should work as expected. Thankfully, that's pretty much the extent of the odd cases in dateperiod arithmetic when dealing with time in UT (avoiding the "joys" of dealing with daylight savings, leap seconds, etc.).
As a bonus, all period arithmetic objects work directly with ranges:
julia> dr = Date(2014,1,29):Day(1):Date(2014,2,3) 20140129:1 day:20140203 julia> collect(dr) 6element Array{Date,1}: 20140129 20140130 20140131 20140201 20140202 20140203 julia> dr = Date(2014,1,29):Dates.Month(1):Date(2014,07,29) 20140129:1 month:20140729 julia> collect(dr) 7element Array{Date,1}: 20140129 20140228 20140329 20140429 20140529 20140629 20140729
As convenient as dateperiod arithmetic is, often the kinds of calculations needed on dates take on a calendrical or temporal nature rather than a fixed number of periods. Holidays are a perfect example; most follow rules such as "Memorial Day = Last Monday of May", or "Thanksgiving = 4th Thursday of November". These kinds of temporal expressions deal with rules relative to the calendar, like first or last of the month, next Tuesday, or the first and third Wednesdays, etc.
The Dates
module provides the adjuster API through several convenient methods that aid in simply and succinctly expressing temporal rules. The first group of adjuster methods deal with the first and last of weeks, months, quarters, and years. They each take a single TimeType
as input and return or adjust to the first or last of the desired period relative to the input.
julia> Dates.firstdayofweek(Date(2014,7,16)) # Adjusts the input to the Monday of the input's week 20140714 julia> Dates.lastdayofmonth(Date(2014,7,16)) # Adjusts to the last day of the input's month 20140731 julia> Dates.lastdayofquarter(Date(2014,7,16)) # Adjusts to the last day of the input's quarter 20140930
The next two higherorder methods, tonext
, and toprev
, generalize working with temporal expressions by taking a DateFunction
as first argument, along with a starting TimeType
. A DateFunction
is just a function, usually anonymous, that takes a single TimeType
as input and returns a Bool
, true
indicating a satisfied adjustment criterion. For example:
julia> istuesday = x>Dates.dayofweek(x) == Dates.Tuesday; # Returns true if the day of the week of x is Tuesday julia> Dates.tonext(istuesday, Date(2014,7,13)) # 20140713 is a Sunday 20140715 julia> Dates.tonext(Date(2014,7,13), Dates.Tuesday) # Convenience method provided for day of the week adjustments 20140715
This is useful with the doblock syntax for more complex temporal expressions:
julia> Dates.tonext(Date(2014,7,13)) do x # Return true on the 4th Thursday of November (Thanksgiving) Dates.dayofweek(x) == Dates.Thursday && Dates.dayofweekofmonth(x) == 4 && Dates.month(x) == Dates.November end 20141127
The Base.filter
method can be used to obtain all valid dates/moments in a specified range:
# Pittsburgh street cleaning; Every 2nd Tuesday from April to November # Date range from January 1st, 2014 to January 1st, 2015 julia> dr = Dates.Date(2014):Day(1):Dates.Date(2015); julia> filter(dr) do x Dates.dayofweek(x) == Dates.Tue && Dates.April <= Dates.month(x) <= Dates.Nov && Dates.dayofweekofmonth(x) == 2 end 8element Array{Date,1}: 20140408 20140513 20140610 20140708 20140812 20140909 20141014 20141111
Additional examples and tests are available in stdlib/Dates/test/adjusters.jl
.
Periods are a human view of discrete, sometimes irregular durations of time. Consider 1 month; it could represent, in days, a value of 28, 29, 30, or 31 depending on the year and month context. Or a year could represent 365 or 366 days in the case of a leap year. Period
types are simple Int64
wrappers and are constructed by wrapping any Int64
convertible type, i.e. Year(1)
or Month(3.0)
. Arithmetic between Period
of the same type behave like integers, and limited PeriodReal
arithmetic is available. You can extract the underlying integer with Dates.value
.
julia> y1 = Dates.Year(1) 1 year julia> y2 = Dates.Year(2) 2 years julia> y3 = Dates.Year(10) 10 years julia> y1 + y2 3 years julia> div(y3,y2) 5 julia> y3  y2 8 years julia> y3 % y2 0 years julia> div(y3,3) # mirrors integer division 3 years julia> Dates.value(Dates.Millisecond(10)) 10
Date
and DateTime
values can be rounded to a specified resolution (e.g., 1 month or 15 minutes) with floor
, ceil
, or round
:
julia> floor(Date(1985, 8, 16), Dates.Month) 19850801 julia> ceil(DateTime(2013, 2, 13, 0, 31, 20), Dates.Minute(15)) 20130213T00:45:00 julia> round(DateTime(2016, 8, 6, 20, 15), Dates.Day) 20160807T00:00:00
Unlike the numeric round
method, which breaks ties toward the even number by default, the TimeType
round
method uses the RoundNearestTiesUp
rounding mode. (It's difficult to guess what breaking ties to nearest "even" TimeType
would entail.) Further details on the available RoundingMode
s can be found in the API reference.
Rounding should generally behave as expected, but there are a few cases in which the expected behaviour is not obvious.
In many cases, the resolution specified for rounding (e.g., Dates.Second(30)
) divides evenly into the next largest period (in this case, Dates.Minute(1)
). But rounding behaviour in cases in which this is not true may lead to confusion. What is the expected result of rounding a DateTime
to the nearest 10 hours?
julia> round(DateTime(2016, 7, 17, 11, 55), Dates.Hour(10)) 20160717T12:00:00
That may seem confusing, given that the hour (12) is not divisible by 10. The reason that 20160717T12:00:00
was chosen is that it is 17,676,660 hours after 00000101T00:00:00
, and 17,676,660 is divisible by 10.
As Julia Date
and DateTime
values are represented according to the ISO 8601 standard, 00000101T00:00:00
was chosen as base (or "rounding epoch") from which to begin the count of days (and milliseconds) used in rounding calculations. (Note that this differs slightly from Julia's internal representation of Date
s using Rata Die notation; but since the ISO 8601 standard is most visible to the end user, 00000101T00:00:00
was chosen as the rounding epoch instead of the 00001231T00:00:00
used internally to minimize confusion.)
The only exception to the use of 00000101T00:00:00
as the rounding epoch is when rounding to weeks. Rounding to the nearest week will always return a Monday (the first day of the week as specified by ISO 8601). For this reason, we use 00000103T00:00:00
(the first day of the first week of year 0000, as defined by ISO 8601) as the base when rounding to a number of weeks.
Here is a related case in which the expected behaviour is not necessarily obvious: What happens when we round to the nearest P(2)
, where P
is a Period
type? In some cases (specifically, when P <: Dates.TimePeriod
) the answer is clear:
julia> round(DateTime(2016, 7, 17, 8, 55, 30), Dates.Hour(2)) 20160717T08:00:00 julia> round(DateTime(2016, 7, 17, 8, 55, 30), Dates.Minute(2)) 20160717T08:56:00
This seems obvious, because two of each of these periods still divides evenly into the next larger order period. But in the case of two months (which still divides evenly into one year), the answer may be surprising:
julia> round(DateTime(2016, 7, 17, 8, 55, 30), Dates.Month(2)) 20160701T00:00:00
Why round to the first day in July, even though it is month 7 (an odd number)? The key is that months are 1indexed (the first month is assigned 1), unlike hours, minutes, seconds, and milliseconds (the first of which are assigned 0).
This means that rounding a DateTime
to an even multiple of seconds, minutes, hours, or years (because the ISO 8601 specification includes a year zero) will result in a DateTime
with an even value in that field, while rounding a DateTime
to an even multiple of months will result in the months field having an odd value. Because both months and years may contain an irregular number of days, whether rounding to an even number of days will result in an even value in the days field is uncertain.
See the API reference for additional information on methods exported from the Dates
module.
Dates.Period
Type
Period Year Month Week Day Hour Minute Second Millisecond Microsecond Nanosecond
Period
types represent discrete, human representations of time.
Dates.CompoundPeriod
Type
CompoundPeriod
A CompoundPeriod
is useful for expressing time periods that are not a fixed multiple of smaller periods. For example, "a year and a day" is not a fixed number of days, but can be expressed using a CompoundPeriod
. In fact, a CompoundPeriod
is automatically generated by addition of different period types, e.g. Year(1) + Day(1)
produces a CompoundPeriod
result.
Dates.Instant
Type
Instant
Instant
types represent integerbased, machine representations of time as continuous timelines starting from an epoch.
Dates.UTInstant
Type
UTInstant{T}
The UTInstant
represents a machine timeline based on UT time (1 day = one revolution of the earth). The T
is a Period
parameter that indicates the resolution or precision of the instant.
Dates.TimeType
Type
TimeType
TimeType
types wrap Instant
machine instances to provide human representations of the machine instant. Time
, DateTime
and Date
are subtypes of TimeType
.
Dates.DateTime
Type
DateTime
DateTime
wraps a UTInstant{Millisecond}
and interprets it according to the proleptic Gregorian calendar.
Dates.Date
Type
Date
Date
wraps a UTInstant{Day}
and interprets it according to the proleptic Gregorian calendar.
Dates.Time
Type
Time
Time
wraps a Nanosecond
and represents a specific moment in a 24hour day.
Dates.DateTime
Method
DateTime(y, [m, d, h, mi, s, ms]) > DateTime
Construct a DateTime
type by parts. Arguments must be convertible to Int64
.
Dates.DateTime
Method
DateTime(periods::Period...) > DateTime
Construct a DateTime
type by Period
type parts. Arguments may be in any order. DateTime parts not provided will default to the value of Dates.default(period)
.
Dates.DateTime
Method
DateTime(f::Function, y[, m, d, h, mi, s]; step=Day(1), limit=10000) > DateTime
Create a DateTime
through the adjuster API. The starting point will be constructed from the provided y, m, d...
arguments, and will be adjusted until f::Function
returns true
. The step size in adjusting can be provided manually through the step
keyword. limit
provides a limit to the max number of iterations the adjustment API will pursue before throwing an error (in the case that f::Function
is never satisfied).
Examples
julia> DateTime(dt > Dates.second(dt) == 40, 2010, 10, 20, 10; step = Dates.Second(1)) 20101020T10:00:40 julia> DateTime(dt > Dates.hour(dt) == 20, 2010, 10, 20, 10; step = Dates.Hour(1), limit = 5) ERROR: ArgumentError: Adjustment limit reached: 5 iterations Stacktrace: [...]source
Dates.DateTime
Method
DateTime(dt::Date) > DateTime
Convert a Date
to a DateTime
. The hour, minute, second, and millisecond parts of the new DateTime
are assumed to be zero.
Dates.DateTime
Method
DateTime(dt::AbstractString, format::AbstractString; locale="english") > DateTime
Construct a DateTime
by parsing the dt
date time string following the pattern given in the format
string.
This method creates a DateFormat
object each time it is called. If you are parsing many date time strings of the same format, consider creating a DateFormat
object once and using that as the second argument instead.
Dates.format
Function
format(io::IO, tok::AbstractDateToken, dt::TimeType, locale)
Format the tok
token from dt
and write it to io
. The formatting can be based on locale
.
All subtypes of AbstractDateToken
must define this method in order to be able to print a Date / DateTime object according to a DateFormat
containing that token.
Dates.DateFormat
Type
DateFormat(format::AbstractString, locale="english") > DateFormat
Construct a date formatting object that can be used for parsing date strings or formatting a date object as a string. The following character codes can be used to construct the format
string:
Code  Matches  Comment 

y 
1996, 96  Returns year of 1996, 0096 
Y 
1996, 96  Returns year of 1996, 0096. Equivalent to y

m 
1, 01  Matches 1 or 2digit months 
u 
Jan  Matches abbreviated months according to the locale keyword 
U 
January  Matches full month names according to the locale keyword 
d 
1, 01  Matches 1 or 2digit days 
H 
00  Matches hours 
M 
00  Matches minutes 
S 
00  Matches seconds 
s 
.500  Matches milliseconds 
e 
Mon, Tues  Matches abbreviated days of the week 
E 
Monday  Matches full name days of the week 
yyyymmdd 
19960101  Matches fixedwidth year, month, and day 
Characters not listed above are normally treated as delimiters between date and time slots. For example a dt
string of "19960115T00:00:00.0" would have a format
string like "ymdTH:M:S.s". If you need to use a code character as a delimiter you can escape it using backslash. The date "1995y01m" would have the format "y\ym\m".
Creating a DateFormat object is expensive. Whenever possible, create it once and use it many times or try the dateformat""
string macro. Using this macro creates the DateFormat object once at macro expansion time and reuses it later. see @dateformat_str
.
See DateTime
and format
for how to use a DateFormat object to parse and write Date strings respectively.
Dates.@dateformat_str
Macro
dateformat"Ymd H:M:S"
Create a DateFormat
object. Similar to DateFormat("Ymd H:M:S")
but creates the DateFormat object once during macro expansion.
See DateFormat
for details about format specifiers.
Dates.DateTime
Method
DateTime(dt::AbstractString, df::DateFormat) > DateTime
Construct a DateTime
by parsing the dt
date time string following the pattern given in the DateFormat
object. Similar to DateTime(::AbstractString, ::AbstractString)
but more efficient when repeatedly parsing similarly formatted date time strings with a precreated DateFormat
object.
Dates.Date
Method
Date(y, [m, d]) > Date
Construct a Date
type by parts. Arguments must be convertible to Int64
.
Dates.Date
Method
Date(period::Period...) > Date
Construct a Date
type by Period
type parts. Arguments may be in any order. Date
parts not provided will default to the value of Dates.default(period)
.
Dates.Date
Method
Date(f::Function, y[, m, d]; step=Day(1), limit=10000) > Date
Create a Date
through the adjuster API. The starting point will be constructed from the provided y, m, d
arguments, and will be adjusted until f::Function
returns true
. The step size in adjusting can be provided manually through the step
keyword. limit
provides a limit to the max number of iterations the adjustment API will pursue before throwing an error (given that f::Function
is never satisfied).
Examples
julia> Date(date > Dates.week(date) == 20, 2010, 01, 01) 20100517 julia> Date(date > Dates.year(date) == 2010, 2000, 01, 01) 20100101 julia> Date(date > Dates.month(date) == 10, 2000, 01, 01; limit = 5) ERROR: ArgumentError: Adjustment limit reached: 5 iterations Stacktrace: [...]source
Dates.Date
Method
Date(dt::DateTime) > Date
Convert a DateTime
to a Date
. The hour, minute, second, and millisecond parts of the DateTime
are truncated, so only the year, month and day parts are used in construction.
Dates.Date
Method
Date(d::AbstractString, format::AbstractString; locale="english") > Date
Construct a Date
by parsing the d
date string following the pattern given in the format
string.
This method creates a DateFormat
object each time it is called. If you are parsing many date strings of the same format, consider creating a DateFormat
object once and using that as the second argument instead.
Dates.Date
Method
Date(d::AbstractString, df::DateFormat) > Date
Parse a date from a date string d
using a DateFormat
object df
.
Dates.Time
Method
Time(h, [mi, s, ms, us, ns]) > Time
Construct a Time
type by parts. Arguments must be convertible to Int64
.
Dates.Time
Method
Time(period::TimePeriod...) > Time
Construct a Time
type by Period
type parts. Arguments may be in any order. Time
parts not provided will default to the value of Dates.default(period)
.
Dates.Time
Method
Time(f::Function, h, mi=0; step::Period=Second(1), limit::Int=10000) Time(f::Function, h, mi, s; step::Period=Millisecond(1), limit::Int=10000) Time(f::Function, h, mi, s, ms; step::Period=Microsecond(1), limit::Int=10000) Time(f::Function, h, mi, s, ms, us; step::Period=Nanosecond(1), limit::Int=10000)
Create a Time
through the adjuster API. The starting point will be constructed from the provided h, mi, s, ms, us
arguments, and will be adjusted until f::Function
returns true
. The step size in adjusting can be provided manually through the step
keyword. limit
provides a limit to the max number of iterations the adjustment API will pursue before throwing an error (in the case that f::Function
is never satisfied). Note that the default step will adjust to allow for greater precision for the given arguments; i.e. if hour, minute, and second arguments are provided, the default step will be Millisecond(1)
instead of Second(1)
.
Examples
julia> Dates.Time(t > Dates.minute(t) == 30, 20) 20:30:00 julia> Dates.Time(t > Dates.minute(t) == 0, 20) 20:00:00 julia> Dates.Time(t > Dates.hour(t) == 10, 3; limit = 5) ERROR: ArgumentError: Adjustment limit reached: 5 iterations Stacktrace: [...]source
Dates.Time
Method
Time(dt::DateTime) > Time
Convert a DateTime
to a Time
. The hour, minute, second, and millisecond parts of the DateTime
are used to create the new Time
. Microsecond and nanoseconds are zero by default.
Dates.now
Method
now() > DateTime
Return a DateTime
corresponding to the user's system time including the system timezone locale.
Dates.now
Method
now(::Type{UTC}) > DateTime
Return a DateTime
corresponding to the user's system time as UTC/GMT.
Base.eps
Function
eps(::DateTime) > Millisecond eps(::Date) > Day eps(::Time) > Nanosecond
Returns Millisecond(1)
for DateTime
values, Day(1)
for Date
values, and Nanosecond(1)
for Time
values.
Dates.year
Function
year(dt::TimeType) > Int64
The year of a Date
or DateTime
as an Int64
.
Dates.month
Function
month(dt::TimeType) > Int64
The month of a Date
or DateTime
as an Int64
.
Dates.week
Function
week(dt::TimeType) > Int64
Return the ISO week date of a Date
or DateTime
as an Int64
. Note that the first week of a year is the week that contains the first Thursday of the year, which can result in dates prior to January 4th being in the last week of the previous year. For example, week(Date(2005, 1, 1))
is the 53rd week of 2004.
Examples
julia> Dates.week(Date(1989, 6, 22)) 25 julia> Dates.week(Date(2005, 1, 1)) 53 julia> Dates.week(Date(2004, 12, 31)) 53source
Dates.day
Function
day(dt::TimeType) > Int64
The day of month of a Date
or DateTime
as an Int64
.
Dates.hour
Function
hour(dt::DateTime) > Int64
The hour of day of a DateTime
as an Int64
.
hour(t::Time) > Int64
The hour of a Time
as an Int64
.
Dates.minute
Function
minute(dt::DateTime) > Int64
The minute of a DateTime
as an Int64
.
minute(t::Time) > Int64
The minute of a Time
as an Int64
.
Dates.second
Function
second(dt::DateTime) > Int64
The second of a DateTime
as an Int64
.
second(t::Time) > Int64
The second of a Time
as an Int64
.
Dates.millisecond
Function
millisecond(dt::DateTime) > Int64
The millisecond of a DateTime
as an Int64
.
millisecond(t::Time) > Int64
The millisecond of a Time
as an Int64
.
Dates.microsecond
Function
microsecond(t::Time) > Int64
The microsecond of a Time
as an Int64
.
Dates.nanosecond
Function
nanosecond(t::Time) > Int64
The nanosecond of a Time
as an Int64
.
Dates.Year
Method
Year(v)
Construct a Year
object with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.Month
Method
Month(v)
Construct a Month
object with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.Week
Method
Week(v)
Construct a Week
object with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.Day
Method
Day(v)
Construct a Day
object with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.Hour
Method
Hour(dt::DateTime) > Hour
The hour part of a DateTime as a Hour
.
Dates.Minute
Method
Minute(dt::DateTime) > Minute
The minute part of a DateTime as a Minute
.
Dates.Second
Method
Second(dt::DateTime) > Second
The second part of a DateTime as a Second
.
Dates.Millisecond
Method
Millisecond(dt::DateTime) > Millisecond
The millisecond part of a DateTime as a Millisecond
.
Dates.Microsecond
Method
Microsecond(dt::Time) > Microsecond
The microsecond part of a Time as a Microsecond
.
Dates.Nanosecond
Method
Nanosecond(dt::Time) > Nanosecond
The nanosecond part of a Time as a Nanosecond
.
Dates.yearmonth
Function
yearmonth(dt::TimeType) > (Int64, Int64)
Simultaneously return the year and month parts of a Date
or DateTime
.
Dates.monthday
Function
monthday(dt::TimeType) > (Int64, Int64)
Simultaneously return the month and day parts of a Date
or DateTime
.
Dates.yearmonthday
Function
yearmonthday(dt::TimeType) > (Int64, Int64, Int64)
Simultaneously return the year, month and day parts of a Date
or DateTime
.
Dates.dayname
Function
dayname(dt::TimeType; locale="english") > String
Return the full day name corresponding to the day of the week of the Date
or DateTime
in the given locale
.
Examples
julia> Dates.dayname(Date("20000101")) "Saturday"source
Dates.dayabbr
Function
dayabbr(dt::TimeType; locale="english") > String
Return the abbreviated name corresponding to the day of the week of the Date
or DateTime
in the given locale
.
Examples
julia> Dates.dayabbr(Date("20000101")) "Sat"source
Dates.dayofweek
Function
dayofweek(dt::TimeType) > Int64
Return the day of the week as an Int64
with 1 = Monday, 2 = Tuesday, etc.
.
Examples
julia> Dates.dayofweek(Date("20000101")) 6source
Dates.dayofmonth
Function
dayofmonth(dt::TimeType) > Int64
The day of month of a Date
or DateTime
as an Int64
.
Dates.dayofweekofmonth
Function
dayofweekofmonth(dt::TimeType) > Int
For the day of week of dt
, return which number it is in dt
's month. So if the day of the week of dt
is Monday, then 1 = First Monday of the month, 2 = Second Monday of the month, etc.
In the range 1:5.
Examples
julia> Dates.dayofweekofmonth(Date("20000201")) 1 julia> Dates.dayofweekofmonth(Date("20000208")) 2 julia> Dates.dayofweekofmonth(Date("20000215")) 3source
Dates.daysofweekinmonth
Function
daysofweekinmonth(dt::TimeType) > Int
For the day of week of dt
, return the total number of that day of the week in dt
's month. Returns 4 or 5. Useful in temporal expressions for specifying the last day of a week in a month by including dayofweekofmonth(dt) == daysofweekinmonth(dt)
in the adjuster function.
Examples
julia> Dates.daysofweekinmonth(Date("20050101")) 5 julia> Dates.daysofweekinmonth(Date("20050104")) 4source
Dates.monthname
Function
monthname(dt::TimeType; locale="english") > String
Return the full name of the month of the Date
or DateTime
in the given locale
.
Examples
julia> Dates.monthname(Date("20050104")) "January"source
Dates.monthabbr
Function
monthabbr(dt::TimeType; locale="english") > String
Return the abbreviated month name of the Date
or DateTime
in the given locale
.
Examples
julia> Dates.monthabbr(Date("20050104")) "Jan"source
Dates.daysinmonth
Function
daysinmonth(dt::TimeType) > Int
Return the number of days in the month of dt
. Value will be 28, 29, 30, or 31.
Examples
julia> Dates.daysinmonth(Date("200001")) 31 julia> Dates.daysinmonth(Date("200102")) 28 julia> Dates.daysinmonth(Date("200002")) 29source
Dates.isleapyear
Function
isleapyear(dt::TimeType) > Bool
Return true
if the year of dt
is a leap year.
Examples
julia> Dates.isleapyear(Date("2004")) true julia> Dates.isleapyear(Date("2005")) falsesource
Dates.dayofyear
Function
dayofyear(dt::TimeType) > Int
Return the day of the year for dt
with January 1st being day 1.
Dates.daysinyear
Function
daysinyear(dt::TimeType) > Int
Return 366 if the year of dt
is a leap year, otherwise return 365.
Examples
julia> Dates.daysinyear(1999) 365 julia> Dates.daysinyear(2000) 366source
Dates.quarterofyear
Function
quarterofyear(dt::TimeType) > Int
Return the quarter that dt
resides in. Range of value is 1:4.
Dates.dayofquarter
Function
dayofquarter(dt::TimeType) > Int
Return the day of the current quarter of dt
. Range of value is 1:92.
Base.trunc
Method
trunc(dt::TimeType, ::Type{Period}) > TimeType
Truncates the value of dt
according to the provided Period
type.
Examples
julia> trunc(Dates.DateTime("19960101T12:30:00"), Dates.Day) 19960101T00:00:00source
Dates.firstdayofweek
Function
firstdayofweek(dt::TimeType) > TimeType
Adjusts dt
to the Monday of its week.
Examples
julia> Dates.firstdayofweek(DateTime("19960105T12:30:00")) 19960101T00:00:00source
Dates.lastdayofweek
Function
lastdayofweek(dt::TimeType) > TimeType
Adjusts dt
to the Sunday of its week.
Examples
julia> Dates.lastdayofweek(DateTime("19960105T12:30:00")) 19960107T00:00:00source
Dates.firstdayofmonth
Function
firstdayofmonth(dt::TimeType) > TimeType
Adjusts dt
to the first day of its month.
Examples
julia> Dates.firstdayofmonth(DateTime("19960520")) 19960501T00:00:00source
Dates.lastdayofmonth
Function
lastdayofmonth(dt::TimeType) > TimeType
Adjusts dt
to the last day of its month.
Examples
julia> Dates.lastdayofmonth(DateTime("19960520")) 19960531T00:00:00source
Dates.firstdayofyear
Function
firstdayofyear(dt::TimeType) > TimeType
Adjusts dt
to the first day of its year.
Examples
julia> Dates.firstdayofyear(DateTime("19960520")) 19960101T00:00:00source
Dates.lastdayofyear
Function
lastdayofyear(dt::TimeType) > TimeType
Adjusts dt
to the last day of its year.
Examples
julia> Dates.lastdayofyear(DateTime("19960520")) 19961231T00:00:00source
Dates.firstdayofquarter
Function
firstdayofquarter(dt::TimeType) > TimeType
Adjusts dt
to the first day of its quarter.
Examples
julia> Dates.firstdayofquarter(DateTime("19960520")) 19960401T00:00:00 julia> Dates.firstdayofquarter(DateTime("19960820")) 19960701T00:00:00source
Dates.lastdayofquarter
Function
lastdayofquarter(dt::TimeType) > TimeType
Adjusts dt
to the last day of its quarter.
Examples
julia> Dates.lastdayofquarter(DateTime("19960520")) 19960630T00:00:00 julia> Dates.lastdayofquarter(DateTime("19960820")) 19960930T00:00:00source
Dates.tonext
Method
tonext(dt::TimeType, dow::Int; same::Bool=false) > TimeType
Adjusts dt
to the next day of week corresponding to dow
with 1 = Monday, 2 = Tuesday, etc
. Setting same=true
allows the current dt
to be considered as the next dow
, allowing for no adjustment to occur.
Dates.toprev
Method
toprev(dt::TimeType, dow::Int; same::Bool=false) > TimeType
Adjusts dt
to the previous day of week corresponding to dow
with 1 = Monday, 2 = Tuesday, etc
. Setting same=true
allows the current dt
to be considered as the previous dow
, allowing for no adjustment to occur.
Dates.tofirst
Function
tofirst(dt::TimeType, dow::Int; of=Month) > TimeType
Adjusts dt
to the first dow
of its month. Alternatively, of=Year
will adjust to the first dow
of the year.
Dates.tolast
Function
tolast(dt::TimeType, dow::Int; of=Month) > TimeType
Adjusts dt
to the last dow
of its month. Alternatively, of=Year
will adjust to the last dow
of the year.
Dates.tonext
Method
tonext(func::Function, dt::TimeType; step=Day(1), limit=10000, same=false) > TimeType
Adjusts dt
by iterating at most limit
iterations by step
increments until func
returns true
. func
must take a single TimeType
argument and return a Bool
. same
allows dt
to be considered in satisfying func
.
Dates.toprev
Method
toprev(func::Function, dt::TimeType; step=Day(1), limit=10000, same=false) > TimeType
Adjusts dt
by iterating at most limit
iterations by step
increments until func
returns true
. func
must take a single TimeType
argument and return a Bool
. same
allows dt
to be considered in satisfying func
.
Dates.Period
Method
Year(v) Month(v) Week(v) Day(v) Hour(v) Minute(v) Second(v) Millisecond(v) Microsecond(v) Nanosecond(v)
Construct a Period
type with the given v
value. Input must be losslessly convertible to an Int64
.
Dates.CompoundPeriod
Method
CompoundPeriod(periods) > CompoundPeriod
Construct a CompoundPeriod
from a Vector
of Period
s. All Period
s of the same type will be added together.
Examples
julia> Dates.CompoundPeriod(Dates.Hour(12), Dates.Hour(13)) 25 hours julia> Dates.CompoundPeriod(Dates.Hour(1), Dates.Minute(1)) 1 hour, 1 minute julia> Dates.CompoundPeriod(Dates.Month(1), Dates.Week(2)) 1 month, 2 weeks julia> Dates.CompoundPeriod(Dates.Minute(50000)) 50000 minutessource
Dates.value
Function
Dates.value(x::Period) > Int64
For a given period, return the value associated with that period. For example, value(Millisecond(10))
returns 10 as an integer.
Dates.default
Function
default(p::Period) > Period
Returns a sensible "default" value for the input Period by returning T(1)
for Year, Month, and Day, and T(0)
for Hour, Minute, Second, and Millisecond.
Date
and DateTime
values can be rounded to a specified resolution (e.g., 1 month or 15 minutes) with floor
, ceil
, or round
.
Base.floor
Method
floor(dt::TimeType, p::Period) > TimeType
Return the nearest Date
or DateTime
less than or equal to dt
at resolution p
.
For convenience, p
may be a type instead of a value: floor(dt, Dates.Hour)
is a shortcut for floor(dt, Dates.Hour(1))
.
julia> floor(Date(1985, 8, 16), Dates.Month) 19850801 julia> floor(DateTime(2013, 2, 13, 0, 31, 20), Dates.Minute(15)) 20130213T00:30:00 julia> floor(DateTime(2016, 8, 6, 12, 0, 0), Dates.Day) 20160806T00:00:00source
Base.ceil
Method
ceil(dt::TimeType, p::Period) > TimeType
Return the nearest Date
or DateTime
greater than or equal to dt
at resolution p
.
For convenience, p
may be a type instead of a value: ceil(dt, Dates.Hour)
is a shortcut for ceil(dt, Dates.Hour(1))
.
julia> ceil(Date(1985, 8, 16), Dates.Month) 19850901 julia> ceil(DateTime(2013, 2, 13, 0, 31, 20), Dates.Minute(15)) 20130213T00:45:00 julia> ceil(DateTime(2016, 8, 6, 12, 0, 0), Dates.Day) 20160807T00:00:00source
Base.round
Method
round(dt::TimeType, p::Period, [r::RoundingMode]) > TimeType
Return the Date
or DateTime
nearest to dt
at resolution p
. By default (RoundNearestTiesUp
), ties (e.g., rounding 9:30 to the nearest hour) will be rounded up.
For convenience, p
may be a type instead of a value: round(dt, Dates.Hour)
is a shortcut for round(dt, Dates.Hour(1))
.
julia> round(Date(1985, 8, 16), Dates.Month) 19850801 julia> round(DateTime(2013, 2, 13, 0, 31, 20), Dates.Minute(15)) 20130213T00:30:00 julia> round(DateTime(2016, 8, 6, 12, 0, 0), Dates.Day) 20160807T00:00:00
Valid rounding modes for round(::TimeType, ::Period, ::RoundingMode)
are RoundNearestTiesUp
(default), RoundDown
(floor
), and RoundUp
(ceil
).
Most Period
values can also be rounded to a specified resolution:
Base.floor
Method
floor(x::Period, precision::T) where T <: Union{TimePeriod, Week, Day} > T
Round x
down to the nearest multiple of precision
. If x
and precision
are different subtypes of Period
, the return value will have the same type as precision
.
For convenience, precision
may be a type instead of a value: floor(x, Dates.Hour)
is a shortcut for floor(x, Dates.Hour(1))
.
julia> floor(Dates.Day(16), Dates.Week) 2 weeks julia> floor(Dates.Minute(44), Dates.Minute(15)) 30 minutes julia> floor(Dates.Hour(36), Dates.Day) 1 day
Rounding to a precision
of Month
s or Year
s is not supported, as these Period
s are of inconsistent length.
Base.ceil
Method
ceil(x::Period, precision::T) where T <: Union{TimePeriod, Week, Day} > T
Round x
up to the nearest multiple of precision
. If x
and precision
are different subtypes of Period
, the return value will have the same type as precision
.
For convenience, precision
may be a type instead of a value: ceil(x, Dates.Hour)
is a shortcut for ceil(x, Dates.Hour(1))
.
julia> ceil(Dates.Day(16), Dates.Week) 3 weeks julia> ceil(Dates.Minute(44), Dates.Minute(15)) 45 minutes julia> ceil(Dates.Hour(36), Dates.Day) 2 days
Rounding to a precision
of Month
s or Year
s is not supported, as these Period
s are of inconsistent length.
Base.round
Method
round(x::Period, precision::T, [r::RoundingMode]) where T <: Union{TimePeriod, Week, Day} > T
Round x
to the nearest multiple of precision
. If x
and precision
are different subtypes of Period
, the return value will have the same type as precision
. By default (RoundNearestTiesUp
), ties (e.g., rounding 90 minutes to the nearest hour) will be rounded up.
For convenience, precision
may be a type instead of a value: round(x, Dates.Hour)
is a shortcut for round(x, Dates.Hour(1))
.
julia> round(Dates.Day(16), Dates.Week) 2 weeks julia> round(Dates.Minute(44), Dates.Minute(15)) 45 minutes julia> round(Dates.Hour(36), Dates.Day) 2 days
Valid rounding modes for round(::Period, ::T, ::RoundingMode)
are RoundNearestTiesUp
(default), RoundDown
(floor
), and RoundUp
(ceil
).
Rounding to a precision
of Month
s or Year
s is not supported, as these Period
s are of inconsistent length.
The following functions are not exported:
Dates.floorceil
Function
floorceil(dt::TimeType, p::Period) > (TimeType, TimeType)
Simultaneously return the floor
and ceil
of a Date
or DateTime
at resolution p
. More efficient than calling both floor
and ceil
individually.
floorceil(x::Period, precision::T) where T <: Union{TimePeriod, Week, Day} > (T, T)
Simultaneously return the floor
and ceil
of Period
at resolution p
. More efficient than calling both floor
and ceil
individually.
Dates.epochdays2date
Function
epochdays2date(days) > Date
Take the number of days since the rounding epoch (00000101T00:00:00
) and return the corresponding Date
.
Dates.epochms2datetime
Function
epochms2datetime(milliseconds) > DateTime
Take the number of milliseconds since the rounding epoch (00000101T00:00:00
) and return the corresponding DateTime
.
Dates.date2epochdays
Function
date2epochdays(dt::Date) > Int64
Take the given Date
and return the number of days since the rounding epoch (00000101T00:00:00
) as an Int64
.
Dates.datetime2epochms
Function
datetime2epochms(dt::DateTime) > Int64
Take the given DateTime
and return the number of milliseconds since the rounding epoch (00000101T00:00:00
) as an Int64
.
Dates.today
Function
today() > Date
Return the date portion of now()
.
Dates.unix2datetime
Function
unix2datetime(x) > DateTime
Take the number of seconds since unix epoch 19700101T00:00:00
and convert to the corresponding DateTime
.
Dates.datetime2unix
Function
datetime2unix(dt::DateTime) > Float64
Take the given DateTime
and return the number of seconds since the unix epoch 19700101T00:00:00
as a Float64
.
Dates.julian2datetime
Function
julian2datetime(julian_days) > DateTime
Take the number of Julian calendar days since epoch 47131124T12:00:00
and return the corresponding DateTime
.
Dates.datetime2julian
Function
datetime2julian(dt::DateTime) > Float64
Take the given DateTime
and return the number of Julian calendar days since the julian epoch 47131124T12:00:00
as a Float64
.
Dates.rata2datetime
Function
rata2datetime(days) > DateTime
Take the number of Rata Die days since epoch 00001231T00:00:00
and return the corresponding DateTime
.
Dates.datetime2rata
Function
datetime2rata(dt::TimeType) > Int64
Return the number of Rata Die days since epoch from the given Date
or DateTime
.
Days of the Week:
Variable  Abbr.  Value (Int) 

Monday 
Mon 
1 
Tuesday 
Tue 
2 
Wednesday 
Wed 
3 
Thursday 
Thu 
4 
Friday 
Fri 
5 
Saturday 
Sat 
6 
Sunday 
Sun 
7 
Months of the Year:
Variable  Abbr.  Value (Int) 

January 
Jan 
1 
February 
Feb 
2 
March 
Mar 
3 
April 
Apr 
4 
May 
May 
5 
June 
Jun 
6 
July 
Jul 
7 
August 
Aug 
8 
September 
Sep 
9 
October 
Oct 
10 
November 
Nov 
11 
December 
Dec 
12 
© 2009–2019 Jeff Bezanson, Stefan Karpinski, Viral B. Shah, and other contributors
Licensed under the MIT License.
https://docs.julialang.org/en/v1.2.0/stdlib/Dates/