Source

File: wp-includes/formatting.php

function human_time_diff( $from, $to = 0 ) {
	if ( empty( $to ) ) {
		$to = time();
	}

	$diff = (int) abs( $to - $from );

	if ( $diff < MINUTE_IN_SECONDS ) {
		$secs = $diff;
		if ( $secs <= 1 ) {
			$secs = 1;
		}
		/* translators: Time difference between two dates, in seconds. %s: Number of seconds. */
		$since = sprintf( _n( '%s second', '%s seconds', $secs ), $secs );
	} elseif ( $diff < HOUR_IN_SECONDS && $diff >= MINUTE_IN_SECONDS ) {
		$mins = round( $diff / MINUTE_IN_SECONDS );
		if ( $mins <= 1 ) {
			$mins = 1;
		}
		/* translators: Time difference between two dates, in minutes (min=minute). %s: Number of minutes. */
		$since = sprintf( _n( '%s min', '%s mins', $mins ), $mins );
	} elseif ( $diff < DAY_IN_SECONDS && $diff >= HOUR_IN_SECONDS ) {
		$hours = round( $diff / HOUR_IN_SECONDS );
		if ( $hours <= 1 ) {
			$hours = 1;
		}
		/* translators: Time difference between two dates, in hours. %s: Number of hours. */
		$since = sprintf( _n( '%s hour', '%s hours', $hours ), $hours );
	} elseif ( $diff < WEEK_IN_SECONDS && $diff >= DAY_IN_SECONDS ) {
		$days = round( $diff / DAY_IN_SECONDS );
		if ( $days <= 1 ) {
			$days = 1;
		}
		/* translators: Time difference between two dates, in days. %s: Number of days. */
		$since = sprintf( _n( '%s day', '%s days', $days ), $days );
	} elseif ( $diff < MONTH_IN_SECONDS && $diff >= WEEK_IN_SECONDS ) {
		$weeks = round( $diff / WEEK_IN_SECONDS );
		if ( $weeks <= 1 ) {
			$weeks = 1;
		}
		/* translators: Time difference between two dates, in weeks. %s: Number of weeks. */
		$since = sprintf( _n( '%s week', '%s weeks', $weeks ), $weeks );
	} elseif ( $diff < YEAR_IN_SECONDS && $diff >= MONTH_IN_SECONDS ) {
		$months = round( $diff / MONTH_IN_SECONDS );
		if ( $months <= 1 ) {
			$months = 1;
		}
		/* translators: Time difference between two dates, in months. %s: Number of months. */
		$since = sprintf( _n( '%s month', '%s months', $months ), $months );
	} elseif ( $diff >= YEAR_IN_SECONDS ) {
		$years = round( $diff / YEAR_IN_SECONDS );
		if ( $years <= 1 ) {
			$years = 1;
		}
		/* translators: Time difference between two dates, in years. %s: Number of years. */
		$since = sprintf( _n( '%s year', '%s years', $years ), $years );
	}

	/**
	 * Filters the human readable difference between two timestamps.
	 *
	 * @since 4.0.0
	 *
	 * @param string $since The difference in human readable text.
	 * @param int    $diff  The difference in seconds.
	 * @param int    $from  Unix timestamp from which the difference begins.
	 * @param int    $to    Unix timestamp to end the time difference.
	 */
	return apply_filters( 'human_time_diff', $since, $diff, $from, $to );
}