ISO week reference
Week 51 2025: December 15–21, 2025
Exact Monday-to-Sunday dates for 2025-W51. Use this week as a calendar reference, open it in the planner, or view it in the full 2025 ISO calendar.
Week51
ISO year2025
Weekdays5
QuarterQ4
ISO reference2025-W51
Starts
Ends
Length7 days
Exact dates
Dates in week 51
ISO weeks run Monday through Sunday.
MonDec 152025
TueDec 162025
WedDec 172025
ThuDec 182025
FriDec 192025
SatDec 202025
SunDec 212025
Use this week
Open Week 51 Planner
Turn these dates into a plan
Open a private weekly planner already set to December 15–21, 2025, then add priorities, deadlines, meetings and hourly work blocks.