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 2026 Oct 12 – Oct 18, 2026What week of the year is October 15, 2026?
Week details
Thursday, October 15, 2026 falls in ISO week 42 of 2026. That week runs from Monday Monday, October 12, 2026 to Sunday Sunday, October 18, 2026, and it touches October. The ISO year 2026 has 53 weeks in total, so this is week 42 of 53, or about 79% 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 42 or a sprint that ends in week 44. The week starts in 7 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 41, and the week after is week 43. 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 42 of 2026. On Monday, Monday, October 12, 2026. On Sunday, Sunday, October 18, 2026. 53 ISO weeks. Monday. The week containing the first Thursday of the year. Yes, when January 1 to 3 fall before the first Thursday. The 3rd week of the month, counting by seven-day blocks from the 1st.Frequently asked questions
What week number is October 15, 2026?
When does week 42 of 2026 start?
When does week 42 of 2026 end?
How many weeks are in 2026?
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 15, 2026?: Week 42 ISO week of 2026 — Oct 12 – Oct 18, 2026
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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