ISO week calendar
Week 51 2027
ISO week 51 of 2027 runs from Monday, December 20, 2027 to Sunday, December 26, 2027.
Date Time Encyclopedia answer, with calculation details and assumptions below.
ISO weeks start on Monday and end on Sunday. Week 1 is the week containing the first Thursday of the ISO week-numbering year.
Snapshot
Week 51 2027
ISO week 51 of 2027 runs from Monday, December 20, 2027 to Sunday, December 26, 2027.
ISO weeks start on Monday and end on Sunday. Week 1 is the week containing the first Thursday of the ISO week-numbering year.
- Week starts
- Monday, December 20, 2027
- Week ends
- Sunday, December 26, 2027
- ISO year
- 2027
- Weeks in ISO year
- 52
ISO week 51, 2027
- MonDec 20, 2027Week start
- TueDec 21, 20272027-W51
- WedDec 22, 20272027-W51
- ThuDec 23, 20272027-W51
- FriDec 24, 20272027-W51
- SatDec 25, 20272027-W51
- SunDec 26, 2027Week end
Method
Find the Monday of ISO week 1, then add seven days for each week after it.
ISO week context
Week 51 2027 uses the ISO week-date system: weeks start Monday, end Sunday, and week 1 is tied to the first Thursday of the ISO year.
Compare nearby ISO weeks
Adjacent week pages help verify handoffs between reporting periods, sprints, payroll periods, and weekly plans.
Related Lookups
FAQ
When does this ISO week start?
Week 51 of 2027 starts on Monday, December 20, 2027.
When does this ISO week end?
Week 51 of 2027 ends on Sunday, December 26, 2027.