The current week number, worked out for your own time zone and updated at midnight. Weeks follow ISO 8601, the numbering used in Europe, most of Asia and in business planning worldwide.
Current ISO week number
42
of 2026
Today is Sunday, 18 October 2026.
This week runs Mon 12 Oct – Sun, 18 Oct 2026
Showing the week in UTC; your own time zone is applied as soon as the page has loaded.
Days left this week
0 days
after today; the week ends on Sun 18 Oct
Days left in 2026
74 days
80% of 2026 has passed
Weeks in 2026
53 weeks
A long year: it has 53 ISO weeks.
Day of the year
291
of 365 days in 2026
Other numbering systems
The same day in other week systems
ISO 8601, weeks start on Monday
Week 42Mon 12 Oct – Sun, 18 Oct 2026
US and Canada, weeks start on Sunday
Week 43Sun 18 Oct – Sat, 24 Oct 2026
Middle East, weeks start on Saturday
Week 43Sat 17 Oct – Fri, 23 Oct 2026
In the Sunday-start and Saturday-start systems (the way spreadsheets and much calendar software count them) week 1 is the week that contains 1 January, even if only one day of it falls in the new year, so the number can differ from the ISO week by one or more. Calendars, payroll and schools each pick their own convention: check which one your organisation uses.
Week number lookup
Look up any week
Week number of a date
Week 42 of 2026
Sunday, 18 October 2026 is in ISO week 42, which runs Mon 12 Oct – Sun, 18 Oct 2026.
Sunday-start numbering: week 43. Saturday-start numbering: week 43. Day 291 of 365.
Dates of a week
Mon 12 Oct – Sun, 18 Oct 2026
ISO week 42 of 2026 starts on Monday, 12 October 2026 and ends on Sunday, 18 October 2026.
ISO 8601 numbers the weeks of a year from 1 to 52 or 53. Weeks run from Monday to Sunday, and week 1 is the week that holds the first Thursday of the year, which is also the week that contains 4 January. Each week belongs to the year that contains its Thursday.
Because of that rule the first days of January can fall in week 52 or 53 of the previous year, and the last days of December in week 1 of the next. A year has 53 weeks when 1 January is a Thursday, or a Wednesday in a leap year.
What this page does and does not do
The number is computed from the date on your device, in your device's time zone, with the Gregorian calendar. If your device clock or time zone is wrong the number can be wrong too. Dates before 1583 are not supported. Sources: ISO 8601-1:2019, clause 5.2.4.2 (week calendar); spreadsheet week-numbering systems 1 and 16 for the Sunday-start and Saturday-start values.
Questions
Good to know
What week is it right now?
On 18 October 2026 (UTC) it is week 42 of 2026 in ISO 8601 numbering. The number at the top of this page is calculated in your own time zone and changes at midnight between Sunday and Monday.
How do ISO week numbers work?
Weeks run from Monday to Sunday. Week 1 is the week with the first Thursday of the year (the week that contains 4 January), and every week belongs to the year that holds its Thursday. A year therefore has 52 or 53 weeks.
Which years have 53 weeks?
A year has 53 ISO weeks when 1 January is a Thursday, or a Wednesday in a leap year: 71 years in every 400. Years with 53 weeks around now: 2020, 2026, 2032, 2037.
Is 1 January always in week 1?
No. In ISO numbering 1 January is in week 1 only when it falls on a Monday, Tuesday, Wednesday or Thursday. Otherwise it belongs to week 52 or 53 of the previous year: 1 January 2027 is a Friday, in week 53 of 2026.
Does the US use the same week numbers?
Usually not. The US and Canada start the week on Sunday and call the week that contains 1 January week 1, so the number can differ from the ISO week. Many US businesses do not use week numbers at all, while calendars and planning software in Europe and Asia show ISO weeks. Both are shown above.
How many weeks are in a year?
A year has 52 weeks and one or two days, so ISO years have either 52 or 53 numbered weeks. 2026 has 53.