How to get the start time of the previous month in Haskell?

user_1663462 0
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I'd like to get the "start" time (the time right at the beginning of the month), of the previous month relative to the current time.

How can I do this?

time haskell
1 Answers

Using UTCTime we can define a function:

import Data.Time

getStartOfPreviousMonth :: UTCTime -> UTCTime 
getStartOfPreviousMonth v = do
  let (y,m,_) = (toGregorian $ utctDay v)
  let v' = addGregorianMonthsClip (-1) $ fromGregorian y m 1
  v { utctDay = v'
    , utctDayTime = secondsToDiffTime 0
    }

Which can be used like so:

> import Data.Time
Data.Time> ct <- getCurrentTime
Data.Time> getStartOfPreviousMonth ct
2020-07-01 00:00:00 UTC
user_16634620
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