Week 1, 2027
January 4–10, 2027
Monday January 4 – Sunday January 102027-W01Days 4–10
The seven days
| Date | ISO week date | Day of year | US week | Islamic date (computed) | Holidays and other dates |
|---|---|---|---|---|---|
| Mon, Jan 4 | 2027-W01-1 | 004 | 2 | 26 Rajab 1448 AH | 2nd January (substitute day) (UK: Scotland); Day after New Year's Day (Mondayised) (New Zealand) |
| Tue, Jan 5 | 2027-W01-2 | 005 | 2 | 27 Rajab 1448 AH | |
| Wed, Jan 6 | 2027-W01-3 | 006 | 2 | 28 Rajab 1448 AH | Epiphany (Spain) |
| Thu, Jan 7 | 2027-W01-4 | 007 | 2 | 29 Rajab 1448 AH | |
| Fri, Jan 8 | 2027-W01-5 | 008 | 2 | 30 Rajab 1448 AH | |
| Sat, Jan 9 | 2027-W01-6 | 009 | 2 | 1 Sha'ban 1448 AH | |
| Sun, Jan 10 | 2027-W01-7 | 010 | 3 | 2 Sha'ban 1448 AH |
About week 1
Week 1 is the week with the year’s first Thursday, here Thursday, January 7, 2027. In US numbering, where weeks start on Sunday and the week of January 1 is week 1, Monday to Saturday are US week 2 and Sunday US week 3.
Holidays this week: 2nd January (substitute day) on Mon, Jan 4 in UK: Scotland; Day after New Year's Day (Mondayised) on Mon, Jan 4 in New Zealand; Epiphany on Wed, Jan 6 in Spain. 1 Sha'ban 1448 AH falls on Sat, Jan 9 by the Umm al-Qura calendar (computed). All weeks of 2027 lists the neighbouring weeks.
Week 1 in other years
| Year | Week 1 runs |
|---|---|
| 2025 | Mon, Dec 30 – Sun, Jan 5, 2025 |
| 2026 | Mon, Dec 29 – Sun, Jan 4, 2026 |
| 2027 | Mon, Jan 4 – Sun, Jan 10 |
| 2028 | Mon, Jan 3 – Sun, Jan 9 |
| 2029 | Mon, Jan 1 – Sun, Jan 7 |
| 2030 | Mon, Dec 31 – Sun, Jan 6, 2030 |
In 2028, week 1 runs Mon, Jan 3 – Sun, Jan 9: 364 days later, 1 day earlier in the calendar. Over the 400-year cycle, the Monday of week 1 falls between December 29 and January 4.
By the end of week 1, 10 days of 2027 have passed (2.7% of the year), and 51 ISO weeks of 2027 remain. The week falls in Q1.
Writing week 1
ISO 8601 writes this week as 2027-W01 (basic format 2027W01), from 2027-W01-1 on Monday to -7 on Sunday. The week number page shows the spreadsheet and Python formulas that give these numbers.