Haskell Language Date and Time Adding, Subtracting and Comparing Days
Example
Given a Day, we can perform simple arithmetic and comparisons, such as adding:
import Data.Time
addDays 1 (fromGregorian 2000 1 1)
-- 2000-01-02
addDays 1 (fromGregorian 2000 12 31)
-- 2001-01-01
Subtract:
addDays (-1) (fromGregorian 2000 1 1)
-- 1999-12-31
addDays (-1) (fromGregorian 0 1 1)
-- -0001-12-31
-- wat
and even find the difference:
diffDays (fromGregorian 2000 12 31) (fromGregorian 2000 1 1)
365
note that the order matters:
diffDays (fromGregorian 2000 1 1) (fromGregorian 2000 12 31)
-365
