[Haskell-beginners] Date Time in Haskell

[Max Voit]

On Thu, 14 May 2015 16:27:46 +0530
Dananji Liyanage <dan9131 at gmail.com> wrote:

> Correct me if I'm doing something wrong here. Here's my code:
> 
>            main = do
>                   now <- getCurrentTime
>                   diffUTCTime now bree
>           bree = readMay "1981-06-16 04:35:25" :: UTCTime

There are several problems with that code. First what the compiler is
complaining about: Last statement in a do-block must have type of the
block, in this case IO () - so print it or return ()

For the readMay - this is expected to return Maybe UTCTime. To stuff
this into diffUTCTime you need to get it out of the Maybe.

For my formulation "is expected to" - it won't, as UTCTime has no Read
instance (so you can't call read on it). Take a look at ParseTime and
its buildTime method.

cheers, max