Week Number
A week number is the position of a week within the year, from 1 up to 52 or 53. It is a compact way to name a stretch of time - "week 31" instead of a full date range - which is why teams use it for planning, reporting, and payroll periods.
Two common conventions
- ISO 8601 starts each week on Monday, and week 1 is the week containing the year's first Thursday. This is standard across Europe and most business software.
- North American counts start each week on Sunday and put January 1 in week 1.
Around New Year the two can differ by a week, and even by a year, so it helps to know which one a calendar uses.
Why a year has 52 or 53 weeks
Most years have 52 numbered weeks. A year gains a 53rd when its days run past 52 full weeks, which depends on the weekday January 1 falls on and whether it is a leap year.
How Sandtime.io fits
Sandtime.io records hours as you work and rolls them into weekly reports, so every week has an accurate total. To look up a number, use the week number tool or the ISO week number tool.
Related Terms
A week number frames a weekly goal, the ISO week is its Monday-start standard form, and a reference period often spans a set number of weeks.