← back to tools

Week Number Calculator

What week is any date? What dates fall in week 34? Full year view — for logistics, HR, and planning.

Tool Limitations & Assumptions
  • Two week standards only: ISO 8601 (Monday-start, used in EU, logistics, manufacturing) and US convention (Sunday-start, used in North America). Other regional standards (e.g. Middle Eastern Saturday-start, Islamic calendar weeks) are not supported.
  • ISO week year ≠ calendar year: ISO weeks can belong to a different year than the calendar date. For example, 1 Jan 2016 is ISO Week 53 of 2015. This tool correctly shows the ISO week year, which may differ from the year you picked.
  • US week standard is approximate: There is no single official "US week" standard (unlike ISO 8601). This tool uses the most common convention: Sunday-start, week 1 begins on Jan 1, partial first/last weeks counted. Some payroll or scheduling software may number weeks differently.
  • Year range: Supported years are 1970–2099. Dates outside this range will be rejected.
  • No time zones: All calculations use your browser's local date. If you're near a day boundary (e.g. late at night) results may differ from UTC-based tools.
  • Clipboard copy: The "Copy" button requires your browser to allow clipboard access. If it fails, the result text will be shown in an alert instead.
  • "Today" pill: Uses the date on your device. If your device clock is wrong, results will be off.
Supported range: 1 Jan 1970 – 31 Dec 2099
Quick Jump
Today Next Week Last Week +30 Days −30 Days Year End
Quick Jump
Current Week Prev Week Next Week Q1 Start (W1) Q3 Start (W27)
Week # Starts Ends Month(s) Quarter