Support for 360_day, 365_day, Julian, Proleptic Gregorian calendars

[adrfantini]

Climate models often use different calendars from the one we are used to. Other than the standard R calendar, 360_day, 365_day and 366_day calendars are quite common. The CF-Conventions, which form the basis for the sharing of climate data in the netCDF format, specify the following calendars as possible:

• gregorian or standard
  Mixed Gregorian/Julian calendar as defined by Udunits. This is the default.
• proleptic_gregorian
  A Gregorian calendar extended to dates before 1582-10-15. That is, a year is a leap year if either (i) it is divisible by 4 but not by 100 or (ii) it is divisible by 400.
• noleap or 365_day
  Gregorian calendar without leap years, i.e., all years are 365 days long.
• all_leap or 366_day
  Gregorian calendar with every year being a leap year, i.e., all years are 366 days long.
• 360_day
  All years are 360 days divided into 30 day months.
• julian
  Julian calendar.

In R, support for these calendars is limited but not non existent: the package PCICt includes support and basic arithmetic for these calendars. Would it be possible somehow to include lubridate support for PCICt calendars or objects?

[vspinu]

This is quite out of scope of lubridate. Concretely, what kind of support do you have in mind?

[adrfantini]

I was hoping from #151 that PCICt support could be included, but of course that was a long time ago and priorities might have changed.

what kind of support do you have in mind?

Being able to use lubridate tools with PCICt objects would be cool. With that I mean intervals, time zones management, handy functions like months, days...

[romoxml]

I concur with the OP. It would be incredibly helpful to be able to run a function similar to:

seq.Date(1,500,by="month",cal.format="360_day")

Currently there is not a clean function for creating accurate date sequences with different calendar formats.

[hadley]

This is out of scope for lubridate, but would be a great idea for a new package!