Editing Calendar date (section)

===Week number used===
{{more|ISO week date|Leap week calendar}}
Companies in Europe often use year, week number, and day for planning purposes. So, for example, an event in a project can happen on {{code|w43}} (week 43) or {{code|w43-1}} (Monday, week 43) or, if the year needs to be indicated, on {{code|w0643}} (the year 2006, week 43; i.e., Monday 23{{nbsp}}October{{ndash}}Sunday 29{{nbsp}}October 2006).

An [[ISO week date|ISO week-numbering year]] has 52 or 53 full weeks. That is 364 or 371 days instead of the conventional Gregorian year of 365 or 366 days. These 53 week years occur on all years that have Thursday as 1 January and on leap years that start on Wednesday the 1 January. The extra week is sometimes referred to as a '[[leap week]]', although ISO 8601 does not use this term.