--[[diff

Subtract the date and time value of two dateObject and returns the resulting dateObject.
Syntax
date.diff(var_date1, var_date2)
Arguments
var_date1
Required. a dateObject or parsable date value
var_date2
Required. a dateObject or parsable date value
Returns
Success	The resulting dateObject
Failure	nil.]]
---------------------------------------Example
-- get the days between two dates
d = date.diff("Jan 7 1563", date(1563, 1, 2))
assert(d:spandays()==5)

--[[epoch

Returns dateObject whose date and time value is the Operating System epoch.
Syntax
date.epoch()
Returns
Success	The resulting dateObject
Failure	nil.]]
---------------------------------------Example
assert(date.epoch()==date("jan 1 1970"))


--[[isleapyear

Check if a number or dateObject is a leapyear.
Syntax
date.isleapyear(var_year)
Arguments
var_year
a number or dateObject or parsable date value
Returns
true if var_year leap year. false if var_year not leap year.
Remarks
A leap year in the Gregorian calendar is defined as a year that is evenly divisible by four, except if it is divisible by 100; however, years that are divisible by 400 are leap years.]]
---------------------------------------Example
d = date(1776, 1, 1)
assert(date.isleapyear(d))
assert(date.isleapyear(d:getyear()))
assert(date.isleapyear(1776))