In article
This library looks complicated. I think some tutorial documentation about how to implement the following use cases would be very helpful to people that don't really care about leap seconds, etc.
Also, I see references to POXIS and Unix in System.Time.Calendar. What is the portability of this module? Will it be implemented for Windows?
It needs only localtime_r and gettimeofday, everything else is Haskell. If those exist on Windows, or can be created, then yes. ISSUE: Will the dependence on localtime_r be a problem for older systems?
Use cases (primarily taken from real-world corporate IT applications I have developed) :
* What is the equivalent (or closest aproximation) of the SQL DateTime type (date and time without any timezone information)? What is the equivalent of the SQL Date type (date without any timezone information)?
SQL DateTime: DayAndTime GregorianDay ISSUE: Should I make a type synonym for this? I'd call it "GregorianDayAndTime". SQL Date: GregorianDay Neither include timezone.
* The user enters a date as "7/4/2005." How do I determine if this date is before or after July 1st of this year?
TODO: Parsing
* How do I present the date "July 1st of this year" to the user in M/D/YYYY format?
do now <- getCalendarTime let thisYear = ctYear now let day = GregorianDay thisYear 7 1 return (formatTime defaultTimeLocale "%m/%d/%Y" day) This actually gives "07/01/2005" rather than "7/1/2005". ISSUE: Should I make additional %-codes for this?
* How do I truncate a datetime to midnight of the same day?
datetime{dtTime = midnight}
How do I truncate a date to the first of the month?
date{gregDay = 1}
How do I truncate a date to the first day of the year it occurred in?
date{gregMonth = 1,gregDay = 1}
* Given a date X, how do I find the last day of the month that X occurs in. For example, If X is July 4th, 2005, then I want the result to be July 31st, 2005. If X is Februrary 5, then I want the result to be Februrary 28 for non-leap-years and February 29 for leap years.
This one's ugly: lastOfTheMonth (GregorianDay y m _) = let m' = (m % 12) + 1 y' = if m == 12 then y + 1 else y day = (GregorianDay y' m' 1) in encodeDay ((decodeDay day) - 1) ISSUE: What kind of "Gregorian arithmetic" should I add, if any?
* The user enters a time T with no date, e.g. "17:30". How do I merge this time onto a date D (e.g. July 4, 2005), so that the result has is a datetime with date D and the time T (July 4, 2005 at 17:30).
DayAndTime d t
* Given two datetimes T1, T2, how do I determine if they are on the same date?
dtDay t1 == dtDay t2 Thanks, these are really good. -- Ashley Yakeley, Seattle WA