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std.dato

ReferenceBy the Norscode project

std.dato works with calendar dates in a way that avoids the most common mistakes. A date is simply an integer — an ordinal counting days — so there is no time zone or clock to trip over.

std.dato works with calendar dates in a way that avoids the most common mistakes. A date is simply an integer — an ordinal counting days — and because there is no time zone or clock involved, you escape the errors that otherwise come from daylight saving and different zones.

The module converts between ordinals and year/month/day and ISO format, adds and subtracts days, months and years, compares two dates, and answers calendar questions such as weekday, week number, quarter and whether a day is a weekend. All expressed as ordinary arithmetic with integers.

When to use it

Use std.dato for anything to do with calendar dates: working out a due date, finding the next working day, counting days between two events, or displaying a date nicely. By using ordinals you avoid the errors that come from time zones and daylight saving.

Getting started

bruk std.dato som dato

funksjon start() -> heiltall {
    la i_dag = dato.frå_ymd(2026, 8, 30)
    la forfall = dato.pluss_dagar(i_dag, 14)   // two weeks ahead
    skriv(dato.til_iso(forfall))                // "2026-09-13"
    skriv(dato.veekedag_namn(forfall))
    returner 0
}

Because dates are integers, "two weeks ahead" is just an addition. til_iso and veekedag_namn make the ordinal readable again.

The functions

Converting

Dates live as ordinals internally, but you want to read and write them as year/month/day or ISO text. These functions go both ways: frå_ymd and frå_iso in to an ordinal, til_ymd, til_iso and til_lang_format back out.

  • frå_ymd(år: heltall, månad: heltall, dag: heltall) -> heltall — Makes an ordinal from year, month and day.
  • til_ymd(ordinal: heltall) -> liste_heltall — Turns an ordinal into [year, month, day].
  • frå_ordinal(ordinal: heltall) -> liste_heltall — Turns an ordinal into [year, month, day].
  • til_ordinal(år: heltall, månad: heltall, dag: heltall) -> heltall — Turns year, month and day into an ordinal (a day count).
  • frå_iso(s: tekst) -> heltall — Interprets an ISO date (YYYY-MM-DD) and returns an ordinal.
  • til_iso(ordinal: heltall) -> tekst — Formats an ordinal as an ISO date.
  • til_lang_format(ordinal: heltall) -> tekst — Formats the date in a long, readable Norwegian format.

Calculating

Because a date is an integer, arithmetic is easy. Add or subtract days, months and years, count the days between two dates, or get the whole list of dates in an interval — with kvardagar_mellom including only the weekdays.

  • pluss_dagar(ordinal: heltall, dagar: heltall) -> heltall — Returns the date a given number of days later.
  • minus_dagar(ordinal: heltall, dagar: heltall) -> heltall — Returns the date a given number of days earlier.
  • pluss_månader(ordinal: heltall, månader: heltall) -> heltall — Returns the date a given number of months later.
  • pluss_år(ordinal: heltall, år: heltall) -> heltall — Returns the date a given number of years later.
  • dagar_mellom(frå: heltall, mål: heltall) -> heltall — Number of days between two dates.
  • datoar_mellom(frå: heltall, mål: heltall) -> liste_heltall — A list of all the dates between two dates.
  • kvardagar_mellom(frå: heltall, mål: heltall) -> liste_heltall — A list of only the weekdays between two dates.

Comparing

Three small functions to decide order: is a before, after or the same day as b.

  • er_før(a: heltall, b: heltall) -> bool — True if a is before b.
  • er_etter(a: heltall, b: heltall) -> bool — True if a is after b.
  • er_lik_dato(a: heltall, b: heltall) -> bool — True if the two dates are the same day.

Calendar info

Everything you can ask the calendar: weekday and week number, whether it is a weekend, which quarter, day of the year, first and last day of the month, and whether the year is a leap year.

  • veekedag(ordinal: heltall) -> heltall — The weekday as a number.
  • veekedag_namn(ordinal: heltall) -> tekst — The weekday's name.
  • er_helg(ordinal: heltall) -> bool — True if the date falls on a Saturday or Sunday.
  • er_kvardag(ordinal: heltall) -> bool — True if the date is a weekday.
  • månadsnamn(månad: heltall) -> tekst — The name of the month.
  • veeke_nummer(ordinal: heltall) -> heltall — The week number the date falls in.
  • kvartal(ordinal: heltall) -> heltall — The quarter (1–4) the date falls in.
  • dag_i_år(ordinal: heltall) -> heltall — Which day of the year the date is (1–366).
  • første_i_månaden(ordinal: heltall) -> heltall — The ordinal for the first day of the same month.
  • siste_i_månaden(ordinal: heltall) -> heltall — The ordinal for the last day of the same month.
  • er_skotår(år: heltall) -> bool — True if the year is a leap year.
  • dagar_i_år(år: heltall) -> heltall — Number of days in the year (365 or 366).
  • dagar_i_månad(år: heltall, månad: heltall) -> heltall — Number of days in the given month.

Good to know

  • An "ordinal" is just an integer counting days, so you can compare two dates with ordinary operators or er_før/er_etter.
  • The module handles calendar dates, not clock times and time zones — which is exactly why you escape a whole class of bugs.
  • dagar_mellom and datoar_mellom are useful for working out periods, for example the number of working days until a deadline.

std.dato is one of the modules in the standard library. Everything ships with the runtime — no installation, no external dependencies. See also Documentation for the language and the runtime.

Related

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