.. _library_dates:

dates

The date object implements some useful calendar date predicates.

It also provides portable predicates for date-time handling, including:

• Unix epoch conversions (data_time_to_unix/2, unix_to_data_time/2)
• date-time arithmetic with durations (add_duration/3, subtract_duration/3, duration_between/3)
• UTC/local conversion using explicit offsets (utc_to_local/3, local_to_utc/3)
• calendar utilities (day_of_year/2, week_of_year_iso/2, weekday/2)
• date-time normalization and validation (normalize_data_time/2, valid_data_time/1-2)

  Date-time values are represented using the date_time/6 compound term:

• date_time(Year, Month, Day, Hours, Minutes, Seconds) The time object implements some useful time predicates.

  Please note that the functionality of these objects depends on the chosen Prolog support for accessing the operating system time and date.

API documentation

Open the `../../apis/library_index.html#dates <../../apis/library_index.html#dates>`__ link in a web browser.

Loading

To load all entities in this library, load the loader.lgt utility file:

::

| ?- logtalk_load(dates(loader)).

Testing

To test this library predicates, load the tester.lgt file:

::

| ?- logtalk_load(dates(tester)).