How to convert Unix timestamp to Datetime in Haskell

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    import Data.Time.Clock.POSIX (posixSecondsToUTCTime)
    import Data.Time.Format (formatTime, defaultTimeLocale)
    
    -- Convert Unix timestamp to DateTime (2020 timestamp)
    unixTimestamp :: Integer
    unixTimestamp = 988159889
    
    dateTime :: UTCTime
    dateTime = posixSecondsToUTCTime (fromInteger unixTimestamp)
    
    main :: IO ()
    main = putStrLn $ "Converted Date: " ++ formatTime defaultTimeLocale "%Y-%m-%d %H:%M:%S" dateTime

Output:

Converted Date: 2001-04-25 00:51:29

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

Code Explanation

To convert a Unix timestamp to a date using Haskell we can use the posixSecondsToUTCTime function to convert the timestamp into a UTCTime object and then use formatTime to format it into a human-readable string.
In this example the Unix timestamp given, '988159889', corresponds to '2001-04-25 00:51:29' UTC.

Convert Date to Unix timestamp in Haskell

Other useful Haskell date functions

Function	Description	Example
`getCurrentTime`	Returns the current UTC time as a `UTCTime` object.	`getCurrentTime` returns 2024-08-28 12:34:56 UTC
`posixSecondsToUTCTime`	Converts a Unix timestamp (POSIX time) to a `UTCTime` object.	`posixSecondsToUTCTime 1652602245` returns 2022-05-15 08:10:45 UTC
`utcTimeToPOSIXSeconds`	Converts a `UTCTime` object to a Unix timestamp (POSIX time) in seconds.	`utcTimeToPOSIXSeconds dateTime` returns 1652602245
`fromGregorian`	Creates a `Day` (date) from a Gregorian year, month, and day.	`fromGregorian 2022 5 15` returns 2022-05-15
`UTCTime`	Constructs a UTC time from a `Day` and a `DiffTime`.	`UTCTime (fromGregorian 2022 5 15) (secondsToDiffTime 30645)` creates 2022-05-15 08:10:45 UTC
`formatTime`	Formats a `UTCTime` or `Day` as a string using a specified format.	`formatTime defaultTimeLocale "%Y-%m-%d %H:%M:%S" dateTime` returns 2022-05-15 08:10:45
`addUTCTime`	Adds a number of seconds to a `UTCTime` object.	`addUTCTime 3600 dateTime` adds 1 hour to the date.
`diffUTCTime`	Calculates the difference in seconds between two `UTCTime` objects.	`diffUTCTime time1 time2` returns the difference in seconds between two times.
`secondsToDiffTime`	Converts a number of seconds to a `DiffTime` object (used for times in `UTCTime`).	`secondsToDiffTime 30645` returns 8 hours, 30 minutes, and 45 seconds.
`getZonedTime`	Returns the current local time and time zone as a `ZonedTime` object.	`getZonedTime` returns the current local time with time zone information.

Current Unix Timestamp SECONDS SINCE JAN 01 1970

Current UTC Time

2025-08-20