The calendar defined in the ISO standards 8601 is commonly referred to as the ISO calendar. The ISO calendar corresponds with the Gregorian (Western) calendar and uses the same year number, but its length is defined to be an integral number of weeks.
The week in the ISO calendar is defined as seven calendar days starting with a Monday. The DI Solution and MS Excel weeks start with a Sunday.
The numbering of the ISO calendar weeks is defined as:
- The first week of a year includes the first Thursday of that year.
- The last week of a year is the week immediately preceding the first calendar week of the next calendar year.
- As Thursday is the “middle day” of the ISO week, each Thursday in a Gregorian calendar year belongs to the same ISO calendar year. If a Gregorian year contains 52 Thursdays, the corresponding ISO calendar year has 52 weeks; if the Gregorian year contains 53 Thursdays, the corresponding ISO calendar year has 53 weeks.
See also:
- Integrator Date Functions in Integrator
- Spectre Date and Time Functions
- Spectre Calendar and Period Types
- Integrator Date Considerations