Weeknumber.io

ISO week 2027-W01

Week 1, 2027

Monday, January 4 – Sunday, January 10, 2027

ISO week 1 of 2027 (2027-W01) runs from Monday, January 4, 2027 to Sunday, January 10, 2027.

This week starts 12 weeks from now. The current week is week 42, 2026.

The 7 days of week 1

DayDateDay of yearUS weekISO date
Monday4 of 36522027-W01-1
Tuesday5 of 36522027-W01-2
Wednesday6 of 36522027-W01-3
Thursday7 of 36522027-W01-4
Friday8 of 36522027-W01-5
Saturday9 of 36522027-W01-6
Sunday10 of 36532027-W01-7

Week 1 at a glance

ISO code
2027-W01 (Monday is 2027-W01-1, Sunday is 2027-W01-7)
Month
January
Quarter
Q1 of 2027
Day of year
Days 4–10 of 365
US week number
Monday–Saturday: US week 2; Sunday: US week 3 (Sunday-start weeks, week 1 contains January 1)
Even or odd
Week 1 is an odd week
Weeks left
After this week, 51 ISO weeks remain in 2027 (52 weeks in total)
Year progress
By Sunday, 3% of 2027 has passed

Holidays and key dates

There are no US federal holidays, daylight saving time changes or quarter starts in week 1 of 2027.

Why week 1 starts here

Week 1 is the week that contains the first Thursday of 2027 (Thursday, January 7, 2027). That is the same as saying it is the week containing January 4.

January 1–3, 2027 still belong to the last ISO week of 2026 (2026-W53).

Week numbers follow ISO 8601: weeks start on Monday and week 1 contains the first Thursday of the year. US weeks start on Sunday, with week 1 containing January 1.

Questions about week 1, 2027

What are the dates of week 1 in 2027?
Week 1 of 2027 starts on Monday, January 4, 2027 and ends on Sunday, January 10, 2027.
What month is week 1 of 2027?
Week 1 falls in January. By the Thursday rule that ISO 8601 uses for years and quarters, it counts as a January week.
How do I get week 1 of 2027 in Excel or Google Sheets?
=ISOWEEKNUM(DATE(2027,1,4)) returns 1. To go the other way, =DATE(2027,1,4)-WEEKDAY(DATE(2027,1,4),2)+1+(1-1)*7 returns the Monday, January 4, 2027.