Date to Week Number Converter
Convert a date to its week number, week-based year, weekday, week start and end dates, and planning metadata.
2027-01-01 falls in ISO Week 53 of 2026 (2026-W53-5), from 2026-12-28 through 2027-01-03.
- Date
- 2027-01-01
- Week system
- ISO
- ISO week date
- 2026-W53-5
- Week-based year
- 2026
- Week number
- 53
- Week starts
- 2026-12-28
- Week ends
- 2027-01-03
- Day of year
- 1
- Quarter
- Q1
- Weeks remaining
- 0
- Excel formula
- =ISOWEEKNUM(DATE(2027,01,01))
Public holidays this week
Country: Holiday country unavailable
Holiday country could not be inferred from this time zone yet.
Copy this result
Copy the calculated week result or a shareable URL with this date, time zone, and week system.
Continue planning this ISO week
2026-W53 runs from 2026-12-28 to 2027-01-03. Open all seven dates, download a calendar event, or use the ISO week-year in your spreadsheet.
ISO date-to-week examples around New Year
The ISO week-year can differ from the calendar year. January 1–3, 2027 belong to 2026-W53; 2027-W01 starts on Monday, January 4. These fixed examples use UTC and ISO weeks.
| Calendar date | ISO week-year and week | Monday–Sunday date range |
|---|---|---|
| Try 2027-01-01 | 2026-W53 | 2026-12-28 to 2027-01-03 |
| Try 2027-01-04 | 2027-W01 | 2027-01-04 to 2027-01-10 |