Week Number Calculator
Worked example result
| ISO week number | 1 |
| ISO week year | 2,026 |
| Day of year | 1 |
January 1, 2026 is a Thursday, so it falls in ISO week 1 of 2026 — the first day of the year is also day 1 of week 1.
Shift the date to the Thursday of its week; Week = 1 + whole weeks between that Thursday and the first Thursday of the ISO year · Powered by CalcHub — Week Number Calculator