2027 has 52 ISO weeks and 2026 has 53. Week 1 is the week that contains the first Thursday of January, and every week runs Monday to Sunday.
| Week | Monday | Sunday |
|---|---|---|
| 1 | Jan 4, 2027 | Jan 10, 2027 |
| 2 | Jan 11, 2027 | Jan 17, 2027 |
| 3 | Jan 18, 2027 | Jan 24, 2027 |
| 4 | Jan 25, 2027 | Jan 31, 2027 |
| 5 | Feb 1, 2027 | Feb 7, 2027 |
| 6 | Feb 8, 2027 | Feb 14, 2027 |
| 7 | Feb 15, 2027 | Feb 21, 2027 |
| 8 | Feb 22, 2027 | Feb 28, 2027 |
| 9 | Mar 1, 2027 | Mar 7, 2027 |
| 10 | Mar 8, 2027 | Mar 14, 2027 |
| 11 | Mar 15, 2027 | Mar 21, 2027 |
| 12 | Mar 22, 2027 | Mar 28, 2027 |
| 13 | Mar 29, 2027 | Apr 4, 2027 |
| 14 | Apr 5, 2027 | Apr 11, 2027 |
| 15 | Apr 12, 2027 | Apr 18, 2027 |
| 16 | Apr 19, 2027 | Apr 25, 2027 |
| 17 | Apr 26, 2027 | May 2, 2027 |
| 18 | May 3, 2027 | May 9, 2027 |
| 19 | May 10, 2027 | May 16, 2027 |
| 20 | May 17, 2027 | May 23, 2027 |
| 21 | May 24, 2027 | May 30, 2027 |
| 22 | May 31, 2027 | Jun 6, 2027 |
| 23 | Jun 7, 2027 | Jun 13, 2027 |
| 24 | Jun 14, 2027 | Jun 20, 2027 |
| 25 | Jun 21, 2027 | Jun 27, 2027 |
| 26 | Jun 28, 2027 | Jul 4, 2027 |
| 27 | Jul 5, 2027 | Jul 11, 2027 |
| 28 | Jul 12, 2027 | Jul 18, 2027 |
| 29 | Jul 19, 2027 | Jul 25, 2027 |
| 30 | Jul 26, 2027 | Aug 1, 2027 |
| 31 | Aug 2, 2027 | Aug 8, 2027 |
| 32 | Aug 9, 2027 | Aug 15, 2027 |
| 33 | Aug 16, 2027 | Aug 22, 2027 |
| 34 | Aug 23, 2027 | Aug 29, 2027 |
| 35 | Aug 30, 2027 | Sep 5, 2027 |
| 36 | Sep 6, 2027 | Sep 12, 2027 |
| 37 | Sep 13, 2027 | Sep 19, 2027 |
| 38 | Sep 20, 2027 | Sep 26, 2027 |
| 39 | Sep 27, 2027 | Oct 3, 2027 |
| 40 | Oct 4, 2027 | Oct 10, 2027 |
| 41 | Oct 11, 2027 | Oct 17, 2027 |
| 42 | Oct 18, 2027 | Oct 24, 2027 |
| 43 | Oct 25, 2027 | Oct 31, 2027 |
| 44 | Nov 1, 2027 | Nov 7, 2027 |
| 45 | Nov 8, 2027 | Nov 14, 2027 |
| 46 | Nov 15, 2027 | Nov 21, 2027 |
| 47 | Nov 22, 2027 | Nov 28, 2027 |
| 48 | Nov 29, 2027 | Dec 5, 2027 |
| 49 | Dec 6, 2027 | Dec 12, 2027 |
| 50 | Dec 13, 2027 | Dec 19, 2027 |
| 51 | Dec 20, 2027 | Dec 26, 2027 |
| 52 | Dec 27, 2027 | Jan 2, 2028 |
How it is computed
ISO 8601 weeks start on Monday. Week 1 is the week with the year's first Thursday, so it always contains January 4 and can start in late December. A year has 53 weeks when it starts on a Thursday, or on a Wednesday in a leap year.
FAQ
Why do some calendars show different week numbers?+
US calendars often start weeks on Sunday and count the week of January 1 as week 1. This table uses the ISO 8601 standard used in Europe, in Canada and by most business software.
Can the last days of December be in week 1?+
Yes. If January 1 falls on a Tuesday, Wednesday or Thursday, the days before it in the same Monday-to-Sunday week belong to week 1 of the new year.