This is usually equal to the normal Gregorian year (as returned by
Date.timeGetYear), except as detailed below:
For Thursday, the week-numbering year is always equal to the usual
calendar year. For other days, the number is such that every day
within a complete week (Monday to Sunday) is contained within the
same week-numbering year.
For Monday, Tuesday and Wednesday occurring near the end of the year,
this may mean that the week-numbering year is one greater than the
calendar year (so that these days have the same week-numbering year
as the Thursday occurring early in the next year).
For Friday, Saturday and Sunday occurring near the start of the year,
this may mean that the week-numbering year is one less than the
calendar year (so that these days have the same week-numbering year
as the Thursday occurring late in the previous year).
An equivalent description is that the week-numbering year is equal to
the calendar year containing the majority of the days in the current
week (Monday to Sunday).
Note that January 1 0001 in the proleptic Gregorian calendar is a
Monday, so this function never returns 0.
Returns the ISO 8601 week-numbering year in which the week containing datetime falls.
This function, taken together with Date.timeGetWeekOfYear and Date.timeGetDayOfWeek can be used to determine the full ISO week date on which datetime falls.
This is usually equal to the normal Gregorian year (as returned by Date.timeGetYear), except as detailed below:
For Thursday, the week-numbering year is always equal to the usual calendar year. For other days, the number is such that every day within a complete week (Monday to Sunday) is contained within the same week-numbering year.
For Monday, Tuesday and Wednesday occurring near the end of the year, this may mean that the week-numbering year is one greater than the calendar year (so that these days have the same week-numbering year as the Thursday occurring early in the next year).
For Friday, Saturday and Sunday occurring near the start of the year, this may mean that the week-numbering year is one less than the calendar year (so that these days have the same week-numbering year as the Thursday occurring late in the previous year).
An equivalent description is that the week-numbering year is equal to the calendar year containing the majority of the days in the current week (Monday to Sunday).
Note that January 1 0001 in the proleptic Gregorian calendar is a Monday, so this function never returns 0.