datebook

gleam add gleam_time@1
gleam add datebook@1

An extension library for gleam/time adding week days and some useful algorithms to work with months and calendar dates.

Example

import datebook/date
import datebook/month
import datebook/weekday
import gleam/time/calendar

pub fn main() {
  // Calculate the weekday based on a calendar.Date
  assert weekday.from_date(calendar.Date(2026, calendar.March, 22))
    == weekday.Sunday

  // Get the next and previous weekday, month, or date
  assert weekday.next(weekday.Thursday) == weekday.Friday
  assert month.next(calendar.January) == calendar.February
  assert date.next(calendar.Date(2026, calendar.March, 22))
    == calendar.Date(2026, calendar.March, 23)

  // Get the last day of a month
  assert month.last_day(calendar.February, 2024) == 29

  // Convert a weekday to a number in Europe
  assert weekday.Thursday |> weekday.days_since(weekday.Monday) == 3
  // ...or in Canada
  assert weekday.Thursday |> weekday.days_since(weekday.Sunday) == 4

  // Get a range of dates
  assert date.range(
      calendar.Date(2026, calendar.March, 29),
      calendar.Date(2026, calendar.April, 2),
    )
    == Ok([
      calendar.Date(2026, calendar.March, 29),
      calendar.Date(2026, calendar.March, 30),
      calendar.Date(2026, calendar.March, 31),
      calendar.Date(2026, calendar.April, 1),
      calendar.Date(2026, calendar.April, 2),
    ])
}

Further documentation can be found at https://hexdocs.pm/datebook.

Development

gleam run   # Run the project
gleam test  # Run the tests