tempo/month_year

Functions to use with the MonthYear type in Tempo.

All functions in this module work on the proleptic Gregorian calendar: the twelve Gregorian months in their Gregorian order, rolling over between December and January, with Gregorian leap year rules for February.

Any year value is accepted, not just the 1000 to 9999 range that the tempo/date constructors are limited to.

Values

compare

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pub fn compare(
  a: tempo.MonthYear,
  to b: tempo.MonthYear,
) -> order.Order

Compares two month-year values chronologically on the Gregorian calendar.

Example

tempo.MonthYear(calendar.June, 2024)
|> month_year.compare(to: tempo.MonthYear(calendar.July, 2024))
// -> order.Lt

days_of

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pub fn days_of(my: tempo.MonthYear) -> Int

Returns the number of days in the month, on the proleptic Gregorian calendar. February is 29 days in a Gregorian leap year and 28 otherwise.

Example

tempo.MonthYear(calendar.February, 2024)
|> month_year.days_of
// -> 29

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pub fn next(month: tempo.MonthYear) -> tempo.MonthYear

Returns the next month on the Gregorian calendar, rolling over from December to January of the following year.

Example

tempo.MonthYear(tempo.Jan, 2024)
|> month_year.next
// -> tempo.MonthYear(tempo.Feb, 2024)

tempo.MonthYear(tempo.Dec, 2024)
|> month_year.next
// -> tempo.MonthYear(tempo.Jan, 2025)

prior

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pub fn prior(my: tempo.MonthYear) -> tempo.MonthYear

Returns the previous month on the Gregorian calendar, rolling back from January to December of the preceding year.

Example

tempo.MonthYear(tempo.Jan, 2024)
|> month_year.prior
// -> tempo.MonthYear(tempo.Dec, 2023)

tempo.MonthYear(tempo.Feb, 2024)
|> month_year.prior
// -> tempo.MonthYear(tempo.Jan, 2024)

to_int

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pub fn to_int(my: tempo.MonthYear) -> Int

Returns the month and year as a single sortable integer, year * 100 plus the Gregorian month number.

Example

tempo.MonthYear(calendar.June, 2024)
|> month_year.to_int
// -> 202_406