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.
ISO week of 2027 Sep 27 – Oct 3, 2027What week of the year is October 1, 2027?
Week details
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. 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. 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. 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.Which week is it?
How ISO week numbers work
Planning by week
Nearby weeks
ISO week 39 of 2027. On Monday, Monday, September 27, 2027. On Sunday, Sunday, October 3, 2027. 52 ISO weeks. Monday. The week containing the first Thursday of the year. Yes, when January 1 to 3 fall before the first Thursday. The 1st week of the month, counting by seven-day blocks from the 1st.Frequently asked questions
What week number is October 1, 2027?
When does week 39 of 2027 start?
When does week 39 of 2027 end?
How many weeks are in 2027?
Which day starts the ISO week?
What defines week 1?
Can a date in January belong to the previous year's week?
What week of the month is it?
What Week Is October 1, 2027?: Week 39 ISO week of 2027 — Sep 27 – Oct 3, 2027
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.
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