What week number is it?

How week numbers work

Most diaries, payroll and planning in the UK use the international standard, ISO 8601. Each week starts on a Monday. Week 1 is the week that has the year's first Thursday in it, which is the same as the week with 4 January in it. So week 1 can start in late December, and the last days of December can fall in week 1 of the next year.

When week 1 starts

Work out something else

• How many weeks are in a year?
  52 weeks and a day or two, and which years have 53 week numbers.
• Date calculator: add or take away days
  The date a number of days, weeks, months or years from any date, or before it.
• What day was I born? Day of the week calculator
  The day of the week for any date since 1753.