Week numbers 2027
2027 has 52 ISO weeks: week 1 starts on Monday, January 4, 2027, and the last week ends on Sunday, January 2, 2028. 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
2027 at a glance
- January 1, 2027 is a Friday and still belongs to week 53 of 2026.
- Week 1 runs from Monday, January 4, 2027 to Sunday, January 10, 2027.
- 2027 has 52 ISO weeks. The last week ends on Sunday, January 2, 2028.
- Christmas Eve (December 24) is in week 51; New Year’s Eve is in week 52.
- With the US count (Sunday to Saturday, week 1 contains January 1), 2027 has 53 partial weeks.
Using the overview
The table above lists all weeks of 2027 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 2026, week numbers 2028.
Frequently asked questions
How many weeks are in 2027?
52 ISO weeks. Week 1 starts on Monday, January 4, 2027, week 52 ends on Sunday, January 2, 2028. The US count gives 53 partial weeks.
What week is January 1, 2027?
Week 53 of 2026, because January 1, 2027 is a Friday – ISO week 1 only starts on Monday, January 4, 2027. In the US count it is week 1.
What week number is Christmas 2027?
December 24, 2027 is in ISO week 51; December 31 is in week 52.
Can I import the 2027 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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