Week 1 of 2026

December 29, 2025 (Monday) to January 4, 2026 (Sunday)

← Week 1 of 2026 Week 2 →
ISO Week Number
Week 1
2026 · Week 1 of 53 total weeks

What dates are in Week 1 of 2026?

Week 1 of 2026 runs from December 29, 2025 (Monday) to January 4, 2026 (Sunday). This is the 1th week of the year according to the ISO 8601 standard, in which weeks start on Monday.

Mon
Dec 29
Day 363
Tue
Dec 30
Day 364
Wed
Dec 31
Day 365
Thu
Jan 1
Day 1
Fri
Jan 2
Day 2
Sat
Jan 3
Day 3
Sun
Jan 4
Day 4
Starts December 29, 2025 Monday · Day 363
Ends January 4, 2026 Sunday · Day 4
Duration 7 days 2026 · 53-week year

📅 Nearby weeks in 2026

Week 1Week 2Week 3

📋 All 53 weeks in 2026

12345·678910·1112131415·1617181920·2122232425·2627282930·3132333435·3637383940·4142434445·4647484950·515253

📆 Week 1 in other years

Week 1 · 2025Week 1 · 2027

🔧 Related tools

Week Number Calculator Date to Week 2026 Full Calendar

❓ Related questions about Week 1 of 2026

What day of the week is Dec 29?

Dec 29 is a Monday. It is the first day of Week 1 of 2026.

What day of the week is Jan 4?

Jan 4 is a Sunday. It is the last day of Week 1 of 2026.

What is the ISO week number for Dec 29?

Dec 29 is in Week 1 of 2026 according to ISO 8601.

What is the ISO week number for Jan 4?

Jan 4 is in Week 1 of 2026 according to ISO 8601.

❓ Frequently asked questions about Week 1 of 2026

What dates are in Week 1 of 2026?

Week 1 of 2026 runs from December 29, 2025 to January 4, 2026.

Which day of the year does Week 1 start on?

Week 1 of 2026 starts on December 29, 2025, the 363th day of 2025.

Does Week 1 of 2026 fall entirely within 2026?

Yes, all 7 days of Week 1 of 2026 fall within 2026.

How many weeks are in 2026?

2026 has 53 weeks according to ISO 8601.