Week 39 of 2026 runs September 21 to September 27

ISO week 39 of 2026 begins on Monday, September 21, 2026 and ends on Sunday, September 27, 2026. That is the week in progress right now. The week covers September only.

What dates are in week 39?

Week 39 of 2026 contains September equinox on September 22. The seven dates always run Monday through Sunday, which is the part of ISO 8601 that most often catches people out: a week that starts on Sunday is a different convention and gives a different number.

How ISO week 39 is worked out

ISO 8601 fixes week one as the week containing the first Thursday of January, which is the same as saying the week containing 4 January, or the week holding the majority of its days in the new year. Counting forward from there, week 39 is the 39th Monday-to-Sunday block of 2026, which lands on September 21. All seven dates sit inside 2026, so the ISO year and the calendar year agree for this week.

When is week 39 in other years?

Week 39 shifts by a day or two each year because a year is 52 weeks plus one or two days, so the Monday that opens it moves from September 21 in 2026 to September 27 in 2027.

How far away is week 39?

Today is Wednesday, September 23, 2026, which sits in ISO week 39 of 2026. Week 39 is the week you are in, and it has 4 days left to run after today.

Questions

What dates are in week 39 of 2026?

Monday September 21, 2026 through Sunday September 27, 2026.

What week is it now?

ISO week 39 of 2026. Today is Wednesday, September 23, 2026.

How many weeks does 2026 have?

53. The 2026 week count page explains the rule.

Do ISO weeks start on Monday or Sunday?

Monday. A Sunday-first week is a different convention and can give a different week number for the same date.

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