17 Calendar Query Functions

6.2.901.900

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
(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

1	Time Scale
2	Dates
3	Time-of-Day
4	Combined Date and Time
5	Moments
6	Date and Time Periods
7	Generic Date Operations
8	Generic Time Operations
9	Generic Datetime Operations
10	Generic Moment Operations
11	Date Arithmetic
12	Time Arithmetic
13	Datetime Arithmetic
14	Current Date and Time
15	Formatting and Parsing
16	Time Zones and UTC Offsets
17	Calendar Query Functions
18	Exceptions