Date

An ISO 8601 compliant date type.

Syntax

The date literal consists of the following values, separated by a -:

either a four-digit year or a sign with any number of digits for the year (e.g. +252525 meaning year 252525),
a two-digit month of the year,
and a two-digit day of that month.

Example date literals

2024-03-30
1920-09-21
#!test[read]
#{{
match
  let $x = 2024-03-30;
  let $y = 1920-09-21;
#}}

Example date literals (non-4-digit year)

+20000-01-01
+900-09-21
#!test[read]
#{{
match
  let $x = +20000-01-01;
  let $y = +900-09-21;
#}}

The minimum supported date is January 1, 262144 BCE, and the maximum supported date is December 31, 262142 CE.

A difference between two dates values is a calendar duration between the two, in years, months, and days.

2024-03-30 - 2020-09-21 == P3Y6M9D

#!test[schema]
define
  attribute publish-date value date;

#!test[schema]
#{{
define
  entity article, owns publish-date;
#}}
#!test[write]
insert
  $a isa article, has publish-date 2025-01-10;

#!test[write]
insert
  $_ isa publish-date 2025-01-10;

#!test[schema]
define
  attribute quarter-start value date @values(2025-01-01, 2025-04-01, 2025-07-01, 2025-10-01);

#!test[schema]
define
  entity half-year-report owns quarter-start @values(2025-01-01, 2025-07-01);

#!test[schema]
define
  attribute contract-date value date @range(2020-01-01..2030-12-31);

#!test[schema]
define
  entity active-contract owns contract-date @range(2025-01-01..2030-12-31);

#!test[read]
match
  $a isa article, has publish-date 2025-01-10;