Week numbers 2026
2026 has 53 ISO weeks: week 1 starts on Monday, December 29, 2025, and the last week ends on Sunday, January 3, 2027. The table lists every week with its dates.
Source: IEEE Std 1003.1 (POSIX) – strftime(), %V: ISO 8601 week number. Updated: .
How it is calculated
2026 at a glance
- January 1, 2026 is a Thursday and already falls in week 1.
- Week 1 runs from Monday, December 29, 2025 to Sunday, January 4, 2026.
- 2026 has 53 ISO weeks because the year starts on a Thursday. The last week ends on Sunday, January 3, 2027.
- Christmas Eve (December 24) is in week 52; New Year’s Eve is in week 53.
- With the US count (Sunday to Saturday, week 1 contains January 1), 2026 has 53 partial weeks.
Using the overview
The table above lists all weeks of 2026 with Monday and Sunday; the current week is highlighted. “Print” prints only the table. “Week numbers as calendar file” creates an ICS file with one all-day entry per week (“Week 1”, “Week 2” …) for Outlook, Google or Apple Calendar. The converter above finds the week of any date.
Counting method
ISO 8601: weeks start on Monday, week 1 contains the first Thursday. Today’s week and more background: week number today. Other years: week numbers 2027, week numbers 2028.
Frequently asked questions
How many weeks are in 2026?
53 ISO weeks. Week 1 starts on Monday, December 29, 2025, week 53 ends on Sunday, January 3, 2027. The US count gives 53 partial weeks.
What week is January 1, 2026?
ISO week 1, because January 1, 2026 is a Thursday and that week contains the year’s first Thursday.
What week number is Christmas 2026?
December 24, 2026 is in ISO week 52; December 31 is in week 53.
Can I import the 2026 week numbers into Outlook or Google Calendar?
Yes. “Week numbers as calendar file (ICS)” downloads a file with one all-day event per week. Import it in Outlook via File › Open & Export › Import, or in Google Calendar via Settings › Import.
Sources and legal basis
- IEEE Std 1003.1 (POSIX) – strftime(), %V: ISO 8601 week number
- Microsoft Support: WEEKNUM function (System 1 = US, System 2 = ISO 8601)
- Wikipedia: ISO week date
- IETF RFC 5545 – iCalendar (ICS file format)
As of:
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