Week numbers 2027
All 52 ISO weeks of 2027 with their exact dates. 2027 starts on a Friday, has 365 days, and counts 52 calendar weeks. Week 1 begins Jan 4, 2027; week 52 ends Jan 2, 2028.
2027 has 52 ISO weeks. Week 1: Jan 4 – Jan 10, 2027. Week 52: Dec 27 – Jan 2, 2028.
Week number chart 2027
| Week number | From (Monday) | To (Sunday) | Month | Quarter |
|---|---|---|---|---|
| Week 1 | Jan 4 | Jan 10 | January | Q1 |
| Week 2 | Jan 11 | Jan 17 | January | Q1 |
| Week 3 | Jan 18 | Jan 24 | January | Q1 |
| Week 4 | Jan 25 | Jan 31 | January | Q1 |
| Week 5 | Feb 1 | Feb 7 | February | Q1 |
| Week 6 | Feb 8 | Feb 14 | February | Q1 |
| Week 7 | Feb 15 | Feb 21 | February | Q1 |
| Week 8 | Feb 22 | Feb 28 | February | Q1 |
| Week 9 | Mar 1 | Mar 7 | March | Q1 |
| Week 10 | Mar 8 | Mar 14 | March | Q1 |
| Week 11 | Mar 15 | Mar 21 | March | Q1 |
| Week 12 | Mar 22 | Mar 28 | March | Q1 |
| Week 13 | Mar 29 | Apr 4 | Mar / Apr | Q2 |
| Week 14 | Apr 5 | Apr 11 | April | Q2 |
| Week 15 | Apr 12 | Apr 18 | April | Q2 |
| Week 16 | Apr 19 | Apr 25 | April | Q2 |
| Week 17 | Apr 26 | May 2 | Apr / May | Q2 |
| Week 18 | May 3 | May 9 | May | Q2 |
| Week 19 | May 10 | May 16 | May | Q2 |
| Week 20 | May 17 | May 23 | May | Q2 |
| Week 21 | May 24 | May 30 | May | Q2 |
| Week 22 | May 31 | Jun 6 | May / Jun | Q2 |
| Week 23 | Jun 7 | Jun 13 | June | Q2 |
| Week 24 | Jun 14 | Jun 20 | June | Q2 |
| Week 25 | Jun 21 | Jun 27 | June | Q2 |
| Week 26 | Jun 28 | Jul 4 | Jun / Jul | Q3 |
| Week 27 | Jul 5 | Jul 11 | July | Q3 |
| Week 28 | Jul 12 | Jul 18 | July | Q3 |
| Week 29 | Jul 19 | Jul 25 | July | Q3 |
| Week 30 | Jul 26 | Aug 1 | Jul / Aug | Q3 |
| Week 31 | Aug 2 | Aug 8 | August | Q3 |
| Week 32 | Aug 9 | Aug 15 | August | Q3 |
| Week 33 | Aug 16 | Aug 22 | August | Q3 |
| Week 34 | Aug 23 | Aug 29 | August | Q3 |
| Week 35 | Aug 30 | Sep 5 | Aug / Sep | Q3 |
| Week 36 | Sep 6 | Sep 12 | September | Q3 |
| Week 37 | Sep 13 | Sep 19 | September | Q3 |
| Week 38 | Sep 20 | Sep 26 | September | Q3 |
| Week 39 | Sep 27 | Oct 3 | Sep / Oct | Q3 |
| Week 40 | Oct 4 | Oct 10 | October | Q4 |
| Week 41 | Oct 11 | Oct 17 | October | Q4 |
| Week 42 | Oct 18 | Oct 24 | October | Q4 |
| Week 43 | Oct 25 | Oct 31 | October | Q4 |
| Week 44 | Nov 1 | Nov 7 | November | Q4 |
| Week 45 | Nov 8 | Nov 14 | November | Q4 |
| Week 46 | Nov 15 | Nov 21 | November | Q4 |
| Week 47 | Nov 22 | Nov 28 | November | Q4 |
| Week 48 | Nov 29 | Dec 5 | Nov / Dec | Q4 |
| Week 49 | Dec 6 | Dec 12 | December | Q4 |
| Week 50 | Dec 13 | Dec 19 | December | Q4 |
| Week 51 | Dec 20 | Dec 26 | December | Q4 |
| Week 52 | Dec 27 | Jan 2, 2028 | Dec / Jan | Q4 |
The final week, week 52, runs into 2028: it ends on Jan 2, 2028. Weeks follow ISO 8601 (Monday start, week 1 contains January 4).
2027 week numbers by month
Which ISO weeks fall in each month of 2027, and how many weeks start (on a Monday) in that month.
| Month | Week numbers | Weeks starting | Month starts |
|---|---|---|---|
| January | 53 (2026), 1–4 | 4 | Jan 1 (Fri) |
| February | 5–8 | 4 | Feb 1 (Mon) |
| March | 9–13 | 5 | Mar 1 (Mon) |
| April | 13–17 | 4 | Apr 1 (Thu) |
| May | 17–22 | 5 | May 1 (Sat) |
| June | 22–26 | 4 | Jun 1 (Tue) |
| July | 26–30 | 4 | Jul 1 (Thu) |
| August | 30–35 | 5 | Aug 1 (Sun) |
| September | 35–39 | 4 | Sep 1 (Wed) |
| October | 39–43 | 4 | Oct 1 (Fri) |
| November | 44–48 | 5 | Nov 1 (Mon) |
| December | 48–52 | 4 | Dec 1 (Wed) |
Holidays and key dates 2027 by week number
| Date | Day | ISO week | US week |
|---|---|---|---|
| New Year's Day | Friday, Jan 1, 2027 | Week 53 (2026) | Week 1 |
| Valentine's Day | Sunday, Feb 14, 2027 | Week 6 | Week 8 |
| Easter Sunday | Sunday, Mar 28, 2027 | Week 12 | Week 14 |
| Mother's Day (US) | Sunday, May 9, 2027 | Week 18 | Week 20 |
| Memorial Day (US) | Monday, May 31, 2027 | Week 22 | Week 23 |
| Father's Day (US) | Sunday, Jun 20, 2027 | Week 24 | Week 26 |
| Independence Day (US) | Sunday, Jul 4, 2027 | Week 26 | Week 28 |
| Labor Day (US) | Monday, Sep 6, 2027 | Week 36 | Week 37 |
| Halloween | Sunday, Oct 31, 2027 | Week 43 | Week 45 |
| Thanksgiving (US) | Thursday, Nov 25, 2027 | Week 47 | Week 48 |
| Black Friday | Friday, Nov 26, 2027 | Week 47 | Week 48 |
| Christmas Day | Saturday, Dec 25, 2027 | Week 51 | Week 52 |
| New Year's Eve | Friday, Dec 31, 2027 | Week 52 | Week 53 |
US (Sunday-start) week numbers in 2027
The chart above uses ISO 8601 (Monday start). US calendars, Outlook in US locale and Excel's default
WEEKNUM() count differently: weeks start on Sunday and week 1 is the week containing
January 1. In 2027, US week 1 runs from Sunday, Dec 27, 2026 to Saturday, Jan 2, 2027,
and the year has 53 US week numbers (the last one is partial).
For Monday–Saturday the US week number is 1 higher than the ISO week number (so ISO week 26 is US week 27); on Sundays it is 2 higher. To convert any single date, use the week number calculator — it shows both systems. Background: week start conventions.
Other years
Frequently asked questions
How many weeks does 2027 have?
2027 has 52 ISO weeks. Like most years it has 52 numbered weeks; the nearest 53-week years are 2026, 2032.
When does week 1 of 2027 start?
Week 1 of 2027 runs from Monday, Jan 4, 2027 to Sunday, Jan 10, 2027 — it is the week containing January 4. 2027 itself begins on a Friday.
When does the last week of 2027 end?
Week 52, the final week of 2027, runs from Dec 27, 2027 to Jan 2, 2028.
Is 2027 a leap year?
No — 2027 has 365 days, which is 52 weeks and 1 day.
What week number is Christmas 2027?
Christmas Day 2027 (Saturday, Dec 25, 2027) is in ISO week 51 and US week 52. Thanksgiving (Nov 25, 2027) is in ISO week 47, and July 4 is in ISO week 26.
Do US week numbers differ from ISO week numbers in 2027?
Yes: from Monday to Saturday the US (Sunday-start) week number is 1 higher than the ISO week number in 2027, and 2 higher on Sundays.