8.12
17 Calendar Query Functions
procedure
(leap-year? y) → boolean?
y : exact-integer?
Returns #t if y is a leap year,
#f otherwise.
Examples:
> (leap-year? 1900) #f
> (leap-year? 2000) #t
> (leap-year? 2004) #t
procedure
(days-in-year y) → (or/c 365 366)
y : exact-integer?
Returns the number of days in year y.
Equivalent to: (if (leap-year? y) 366 365)
Examples:
> (days-in-year 1900) 365
> (days-in-year 2000) 366
> (days-in-year 2004) 366
procedure
(days-in-month y m) → (integer-in 28 31)
y : exact-integer? m : (integer-in 1 12)
Returns the number of days in month m in year
y.
Examples:
> (days-in-month 2015 8) 31
> (days-in-month 2015 2) 28
> (days-in-month 2016 2) 29
procedure
(day-of-month/c y m) → flat-contract?
y : exact-integer? m : (integer-in 1 12)
Returns a contract for days in the specified month.
The contract is equivalent to (integer-in 1 (days-in-month y m)).
procedure
(iso-weeks-in-year y) → (or/c 52 53)
y : exact-integer?
Returns the number of weeks in year y, according
to the
ISO
8601 week-numbering year.
Examples:
> (iso-weeks-in-year 2005) 52
> (iso-weeks-in-year 2015) 53