Defined in header <chrono>
class ambiguous_local_time;
(since C++20)

Defines a type of object to be thrown as exception to report that an attempt was made to convert a ambiguous std::chrono::local_time to a std::chrono::sys_time without specifying a std::chrono::choose (such as choose::earliest or choose::latest).

This exception is thrown by std::chrono::time_zone::to_sys and functions that call it (such as the constructors of std::chrono::zoned_time that takes a std::chrono::local_time).

cpp/error/exception cpp/error/runtime errorstd-chrono-ambiguous local time-inheritance.svg

Inheritance diagram.

Member functions

constructs the exception object
(public member function)


template< class Duration >
ambiguous_local_time(const std::chrono::local_time<Duration>& tp,
                     const std::chrono::local_info& i);

Constructs the exception object. The explanatory string returned by what() is equivalent to that produced by os.str() after the following code:

std::ostringstream os;
os << tp << " is ambiguous.  It could be\n"
   << tp << ' ' << i.first.abbrev << " == "
   << tp - i.first.offset << " UTC or\n"
   << tp << ' ' << i.second.abbrev  << " == "
   << tp - i.second.offset  << " UTC";

Because copying a standard library class derived from std::exception is not permitted to throw exceptions, this message is typically stored internally as a separately-allocated reference-counted string.

The behavior is undefined if i.result != std::chrono::local_info::ambiguous.


tp - the time point for which conversion was attempted
i - a std::chrono::local_info describing the result of the conversion attempt


May throw std::bad_alloc.

Inherited from std::exception

Member functions

destroys the exception object
(virtual public member function of std::exception)
returns an explanatory string
(virtual public member function of std::exception)

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