current year and quantity days in month

Question

I have two questions:

How can I get current year (not date) in haskell ?

How can I get quantity days in some month some year ? For example 04.2011 has got 30 days.

Answer 1

This will give you the year, month and day:

import Data.Time.Clock
import Data.Time.Calendar

date :: IO (Integer,Int,Int) -- :: (year,month,day)
date = getCurrentTime >>= return . toGregorian . utctDay

Source: http://www.haskell.org/haskellwiki/Date

There's a function in Date.Time.Calendar called gregorianMonthLength with type Integer -> Int -> Int. It takes a year and a month as arguments, returns the number of days, just like you need. http://www.haskell.org/ghc/docs/7.0.2/html/libraries/time-1.2.0.3/Data-Time-Calendar.html

A full example:

import Data.Time.Clock
import Data.Time.Calendar

date :: IO (Integer,Int,Int) -- :: (year,month,day)
date = getCurrentTime >>= return . toGregorian . utctDay

main = do
    (year, month, day) <- date
    putStrLn $ "Days in this month: " ++ (show $ gregorianMonthLength year month)