What week of the year is October 1, 2027?

Week 39

ISO week of 2027

Sep 27 – Oct 3, 2027

Week details

W39ISO week
Sep 27week starts (Mon)
Oct 3week ends (Sun)
52weeks in 2027
1stweek of the month
Q4quarter
Fridayweekday
356days until week starts

Which week is it?

Friday, October 1, 2027 falls in ISO week 39 of 2027. That week runs from Monday Monday, September 27, 2027 to Sunday Sunday, October 3, 2027, and it touches September and October. The ISO year 2027 has 52 weeks in total, so this is week 39 of 52, or about 75% of the way through the ISO year.

How ISO week numbers work

ISO 8601 weeks begin on Monday, and week 1 is the week that contains the first Thursday of the year. Because of that rule, the first days of January can belong to the last week of the previous year and the last days of December can belong to week 1 of the next. Most years have 52 weeks; roughly every five or six years a 53rd week is added to keep the count aligned with the seasons.

Planning by week

Schedules in manufacturing, logistics, education and project management are often written in week numbers, for example a delivery in week 39 or a sprint that ends in week 41. The week starts in 356 days, so there is time to plan. Keep in mind that US calendars often start the week on Sunday and use a different rule for week 1, so week numbers can differ between countries.

Nearby weeks

The week before is week 38, and the week after is week 40. The year pages list every week with its date range, and the week-number pages link to each of them.

Frequently asked questions

What week number is October 1, 2027?

ISO week 39 of 2027.

When does week 39 of 2027 start?

On Monday, Monday, September 27, 2027.

When does week 39 of 2027 end?

On Sunday, Sunday, October 3, 2027.

How many weeks are in 2027?

52 ISO weeks.

Which day starts the ISO week?

Monday.

What defines week 1?

The week containing the first Thursday of the year.

Can a date in January belong to the previous year's week?

Yes, when January 1 to 3 fall before the first Thursday.

What week of the month is it?

The 1st week of the month, counting by seven-day blocks from the 1st.

RESULT & PLANNING

Use this calculation

What Week Is October 1, 2027?: Week 39 ISO week of 2027 — Sep 27 – Oct 3, 2027

How this calculation was worked out

The result uses the exact inputs on this page and calendar/time arithmetic appropriate to this calculator. The result shown above is the value to use for this calculation.

Working days and weekends

360Calendar days
258Weekdays
51Saturdays
51Sundays
Not included unless this calculator says otherwisePublic holidays

Practical planning milestones

  1. Calculated dateFriday, October 1, 2027

Accuracy and limitations

  • The result uses the calendar rules and time zone shown on this page.
  • Leap years and actual month lengths are handled by the calendar arithmetic where they affect the calculation.

Save or share this result

Calculation history

Machine-readable result
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