# Cookbook/Dates And Time

### From HaskellWiki

< Cookbook

## Contents |

## 1 Finding today's date

import Data.Time c <- getCurrentTime --> 2009-04-21 14:25:29.5585588 UTC (y,m,d) = toGregorian $ utctDay c --> (2009,4,21)

## 2 Adding to or subtracting from a date

Problem | Solution | Examples |
---|---|---|

adding days to a date | addDays | import Data.Time a = fromGregorian 2009 12 31 --> 2009-12-31 b = addDays 1 a --> 2010-01-01 |

subtracting days from a date | addDays | import Data.Time a = fromGregorian 2009 12 31 --> 2009-12-31 b = addDays (-7) a --> 2009-12-24 |

## 3 Difference of two dates

Problem | Solution | Examples |
---|---|---|

calculating the difference of two dates | diffDays | import Data.Time a = fromGregorian 2009 12 31 --> 2009-12-31 b = fromGregorian 2010 12 31 --> 2010-12-31 diffDays b a --> 365 |

## 4 CPU time

Use System.CPUTime.getCPUTime to get the CPU time in picoseconds.

You can time a computation like this

getCPUTimeDouble :: IO Double getCPUTimeDouble = do t <- System.CPUTime.getCPUTime; return ((fromInteger t) * 1e-12) main = do t1 <- getCPUTimeDouble print (fib 30) t2 <- getCPUTimeDouble print (t2-t1)