December 28, 2026 – January 3, 2027
MonTueWedThuFriSatSun
Week 1 contains the first Thursday of the year.ISO guide →Date → week number
December 31, 2026: What week number?
Thursday, December 31, 2026ISO Week 532026-W53
ISO Week 53 runs from December 28, 2026 to January 3, 2027.
ISO vs US-style week numbers
The same date can have different week numbers
ISO weeks start on Monday. The simplified US-style system starts on Sunday and counts the week containing January 1 as Week 1.
December 27, 2026 – January 2, 2027
SunMonTueWedThuFriSat
Week 1 contains January 1.US-style guide →ISO weekWeek 53
US-style weekWeek 53
WeekdayThursday
QuarterQ4
Day of year365 / 365
ISO weekday4 / 7
December 2026
Date context
Thursday, December 31, 2026 is day 365 of 2026 and belongs to ISO Week 53.
This ISO week crosses a month boundary: it starts in December and ends in January.
Distance from today
How long until December 31, 2026?
Days136
Full weeks19
Remaining days3
December 31, 2026 is 136 days from today, equal to 19 full weeks and 3 days.