How to convert Unix timestamp to Datetime in OCaml

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    open Unix

    (* Convert Unix timestamp to Date *)
    let unix_timestamp = 1733127551 (* Unix timestamp as float *)
    let tm = Unix.gmtime unix_timestamp
    
    let () =
        Printf.printf "Converted Date: %04d-%02d-%02d %02d:%02d:%02d\n"
        (tm.tm_year + 1900) (tm.tm_mon + 1) tm.tm_mday
        tm.tm_hour tm.tm_min tm.tm_sec

Output:

Converted Date: 2024-12-02 08:19:11

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

Code Explanation

In this Ocaml snippet, the Unix timestamp 1733127551 is converted to a human-readable date using the Unix.gmtime function, which returns a tm record. This record contains fields such as tm_year, tm_mon, tm_mday, tm_hour, tm_min, and tm_sec. These values are printed in the format yyyy-MM-dd HH:mm:ss using Printf.printf.
The tm_year field contains the number of years since 1900, so 1900 is added to it, and tm_mon is zero-based, so 1 is added.
In this example the result is 2024-12-02 08:19:11.

Convert Date to Unix timestamp in Ocaml

Other useful OCaml date functions

Function	Description	Example
`Unix.time()`	Returns the current Unix timestamp (seconds since 1970-01-01).	`Unix.time()` returns 1693227296.0
`Unix.gmtime()`	Converts a Unix timestamp to a `tm` structure in UTC.	`Unix.gmtime(1589530245.0)` returns the corresponding date and time in UTC.
`Unix.localtime()`	Converts a Unix timestamp to a `tm` structure in the local time zone.	`Unix.localtime(1589530245.0)` returns the date and time in the local time zone.
`Unix.mktime()`	Converts a `tm` structure to a Unix timestamp.	`Unix.mktime(tm)` converts a `tm` structure to a Unix timestamp.
`Unix.strftime()`	Formats a `tm` structure as a string according to the specified format.	`Unix.strftime "%Y-%m-%d" tm` returns "2020-05-15"
`Unix.strptime()`	Parses a date string into a `tm` structure using a format string.	`Unix.strptime "%Y-%m-%d" "2020-05-15"` parses the string into a `tm` structure.
`Unix.sleep()`	Suspends the execution of the program for the specified number of seconds.	`Unix.sleep(5)` suspends the program for 5 seconds.
`Unix.gettimeofday()`	Returns the current time as a floating-point number of seconds since the epoch, including fractional seconds.	`Unix.gettimeofday()` returns 1693227296.123

Current Unix Timestamp SECONDS SINCE JAN 01 1970

Current UTC Time

2025-08-20