Description:
Date fields may have the incorrect year when using ISO week number formatting.

Steps to Reproduce:
* Open LibreOffice Writer
* Create a new document or open an existent one
* Insert a date field. The date field value should be 2025-12-29, 2025-12-30, or 2025-12-31.
* Format the field as:
  - Category: Date
  - Format code: YYYY"W"WW (scroll to "Additional formats…" at the bottom of the list of formats)
* OK all relevant dialogues

Actual Results:
It returns 2025W1

Expected Results:
It should return 2026W01


Reproducible: Always


User Profile Reset: No

Additional Info:
Obviously, the year is off by one. Even though the date *is* in 2025, when used along with the ISO week number, the year should be consistent with the ISO week. Note that it could be:

* One year less than the calendar year (2027-01-02 = 2026W53)
* The same year as the calendar year (2026-12-30 = 2026W53, 2028-12-29 = 2028W52, 2029-01-01 = 2029W01)
* One year more than the calendar year (2025-12-29 = 2026W01)

NB: Note also that the ISO week number is supposed to be written as two digits, so with a "0" prefix if necessary.