How to convert Datetime to Unix timestamp in Prolog

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    :- use_module(library(date)).

    % Convert Date to Unix timestamp
    convert_date_to_unix(Year, Month, Day, Hour, Minute, Second, UnixTimestamp) :-
        date_time_stamp(date(Year, Month, Day, Hour, Minute, Second, 0, 'UTC', -), UnixTimestamp).
    
    % Example usage
    ?- convert_date_to_unix(2019, 6, 24, 18, 30, 22, UnixTimestamp), writeln(UnixTimestamp).

Output:

1561401022

Example only. There may be multiple ways to perform this operation.

Code Explanation

In this Prolog example, the date_time_stamp() predicate converts the given date (2018-07-15 12:30:45) into a Unix timestamp.
The first argument is a date structure, and the second argument is the resulting Unix timestamp. The result is printed using writeln().

Convert Unix timestamp to Date in Prolog

Other useful Prolog date functions

Function	Description	Example
`stamp_date_time(+Stamp, -DateTime, +TimeZone)`	Converts a Unix timestamp to a structured date-time term.	`stamp_date_time(1514764800, DateTime, 'UTC')` returns a date-time structure for 2018-01-01 00:00:00 UTC.
`date_time_stamp(+DateTime, -Stamp)`	Converts a structured date-time term to a Unix timestamp.	`date_time_stamp(date(2018, 7, 15, 12, 30, 45, 0, 'UTC', -), Stamp)` returns the Unix timestamp 1531656645.
`date_time_value(+Component, +DateTime, -Value)`	Extracts the value of a specific component (like year, month, or day) from a structured date-time term.	`date_time_value(year, DateTime, Year)` extracts the year component.
`format_time(-Formatted, +Format, +DateTime)`	Formats a structured date-time term into a string using the given format.	`format_time(atom(Date), '%Y-%m-%d %H:%M:%S', DateTime)` returns 2018-07-15 12:30:45.
`get_time(-Stamp)`	Returns the current Unix timestamp.	`get_time(Stamp)` returns the current Unix timestamp.
`date(+Year, +Month, +Day, +Hour, +Minute, +Second, +Milli, +TimeZone, +DST)`	Represents a structured date-time term in Prolog.	`date(2018, 7, 15, 12, 30, 45, 0, 'UTC', -)` represents the date 2018-07-15 12:30:45 UTC.
`date_time_now(-DateTime)`	Returns the current date and time as a structured date-time term.	`date_time_now(DateTime)` returns the current date and time.
`date_time_value(+Component, +DateTime, -Value)`	Extracts components (year, month, etc.) from a date-time term.	`date_time_value(month, DateTime, Month)` extracts the month from a date-time term.

Current Unix Timestamp SECONDS SINCE JAN 01 1970

Current UTC Time

2025-08-20