Week 39, 2026
September 21–27, 2026
Monday September 21 – Sunday September 272026-W39Days 264–270
The seven days
| Date | ISO week date | Day of year | US week | Islamic date (computed) | Holidays and other dates |
|---|---|---|---|---|---|
| Mon, Sep 21 | 2026-W39-1 | 264 | 39 | 10 Rabi' al-Thani 1448 AH | Respect for the Aged Day (Japan); Yom Kippur |
| Tue, Sep 22 | 2026-W39-2 | 265 | 39 | 11 Rabi' al-Thani 1448 AH | Citizens' Holiday (Japan) |
| Wed, Sep 23 | 2026-W39-3 | 266 | 39 | 12 Rabi' al-Thani 1448 AH | Autumnal Equinox Day (Japan) |
| Thu, Sep 24 | 2026-W39-4 | 267 | 39 | 13 Rabi' al-Thani 1448 AH | Heritage Day (South Africa) |
| Fri, Sep 25 | 2026-W39-5 | 268 | 39 | 14 Rabi' al-Thani 1448 AH | Mid-Autumn Festival |
| Sat, Sep 26 | 2026-W39-6 | 269 | 39 | 15 Rabi' al-Thani 1448 AH | The day following the Chinese Mid-Autumn Festival (Hong Kong) |
| Sun, Sep 27 | 2026-W39-7 | 270 | 40 | 16 Rabi' al-Thani 1448 AH |
About week 39
In US numbering, where weeks start on Sunday and the week of January 1 is week 1, Monday to Saturday are US week 39 and Sunday US week 40.
Holidays this week: Respect for the Aged Day on Mon, Sep 21 in Japan; Citizens' Holiday on Tue, Sep 22 in Japan; Autumnal Equinox Day on Wed, Sep 23 in Japan; Heritage Day on Thu, Sep 24 in South Africa; The day following the Chinese Mid-Autumn Festival on Sat, Sep 26 in Hong Kong. On Sun, Sep 27 clocks in New Zealand go forward one hour at 2:00 a.m. The September equinox is on Wed, Sep 23 at 00:05 UTC. Also this week: Yom Kippur on Mon, Sep 21 (10 Tishrei; begins at sunset the evening before); Mid-Autumn Festival on Fri, Sep 25 (15th day of the 8th lunar month). All weeks of 2026 lists the neighbouring weeks.
Week 39 in other years
| Year | Week 39 runs |
|---|---|
| 2024 | Mon, Sep 23 – Sun, Sep 29 |
| 2025 | Mon, Sep 22 – Sun, Sep 28 |
| 2026 | Mon, Sep 21 – Sun, Sep 27 |
| 2027 | Mon, Sep 27 – Sun, Oct 3 |
| 2028 | Mon, Sep 25 – Sun, Oct 1 |
| 2029 | Mon, Sep 24 – Sun, Sep 30 |
In 2027, week 39 runs Mon, Sep 27 – Sun, Oct 3: 2026 has 53 weeks, so the same number comes 371 days later, 6 days later in the calendar. Over the 400-year cycle, the Monday of week 39 falls between September 20 and September 27.
By the end of week 39, 270 days of 2026 have passed (74.0% of the year), and 14 ISO weeks of 2026 remain. The week falls in Q3.
Writing week 39
ISO 8601 writes this week as 2026-W39 (basic format 2026W39), from 2026-W39-1 on Monday to -7 on Sunday. The week number page shows the spreadsheet and Python formulas that give these numbers.