Template:IsLeapYear/doc
This is a documentation subpage for Template:IsLeapYear. It contains usage information, categories and other content that is not part of the original template page. 
 Usage:

{{IsLeapYearyear}}
 year defaults to
{{CURRENTYEAR}}
= 2017. It must be specified in the Gregorian calendar, extended to all epochs using linear year numbering: use the proleptic Gregorian calendar in Christian Era before the change, and the astronomical year convention (using negative numbers, and year 0) in all years BC before the Christian era (there's a difference of 1 in absolute value).  This template is substitutable.
 Formula:
 Is equivalent to {{#expr: ((({{{1}}}) mod 4 = 0) and (({{{1}}}) mod 100 != 0)) or (({{{1}}}) mod 400 = 0)}}, but for efficiency is currently coded as {{#time:L  1 January {{{1}}} }}
 Sanity check:
 {{ IsLeapYear  2000 }} gives 1: 2000 AD is effectively a leap year (in both the Julian and Gregorian calendars).
 {{ IsLeapYear  502*48 }} gives 1: 2000 AD is effectively a leap year (in both the Julian and Gregorian calendars).
 {{ IsLeapYear  2001 }} gives 0: 2001 AD is not a leap year.
 {{ IsLeapYear  2004 }} gives 1: 2004 AD is a leap year.
 {{ IsLeapYear  2005 }} gives 0: 2005 AD is not a leap year.
 {{ IsLeapYear  2007 }} gives 0: 2007 AD is not a leap year.
 {{ IsLeapYear  2008 }} gives 1: 2008 AD is a leap year.
 {{ IsLeapYear  2009 }} gives 0: 2009 AD is not a leap year.
 {{ IsLeapYear  2100 }} gives 0: 2100 AD is not a leap year in the Gregorian calendar (but not in the Julian calendar).
 {{ IsLeapYear  2400 }} gives 1: 2400 AD is effectively a leap year (in both the Julian and Gregorian calendars).
 {{ IsLeapYear  1900 }} gives 0: 1900 AD is not a leap year in the Gregorian calendar (but not in the Julian calendar).
 {{ IsLeapYear  1800 }} gives 0: 1800 AD is not a leap year in the Gregorian calendar (but not in the Julian calendar).
 {{ IsLeapYear  1700 }} gives 0: 1700 AD is not a leap year in the Gregorian calendar (but not in the Julian calendar).
 {{ IsLeapYear  1600 }} gives 1: 1600 AD is effectively a leap year (in both the Julian and Gregorian calendars).
 {{ IsLeapYear  1500 }} gives 0: 1500 AD is not a leap year in the proleptic Gregorian calendar (but is leap in the actual Julian calendar).
 {{ IsLeapYear  0 }} gives 1: 1 BC is a leap year in the astronomical calendar (mostly pointless for actual calendars of such epoch, but correct in the astronomical calendar where it is year 0).
 {{ IsLeapYear  100 }} gives 0: 101 BC is not a leap year in the astronomical calendar (mostly pointless for actual calendars of such epoch, but correct in the astronomical calendar where it is year 100).
Results for fractions like {{ IsLeapYear  2000.9 }} = 1 are unspecified, even if it apparently gives an "expected" result at the moment this might change without notice.