Microsoft Office Tutorials and References
In Depth Information
in most years, but is 53 every fourth year. This system ensures that a year
is made up of whole seven-day weeks. This is better than the old results of
In the old system with WEEKNUM, the week containing the first of the year
was always labeled as Week 1. If the first fell on a Sunday, and your weeks
started on Monday, then Sunday January 1 is Week 1 and Monday January
2 is Week 2. The possibility of having weeks that last for one day made it
difficult to compare one week to the next. Nonetheless, the Excel team added
new return_types for this system as well. In the past, 1 meant weeks started
on Sunday and 2 meant weeks started on Monday. Now, you can specify weeks
should start on Monday (11), Tuesday (12), and so on, up to Sunday (17).
The WEEKNUM function returns a number that indicates where the week falls
numerically within a year. This function takes the following arguments:
serial_num — This is a date within the week.
return_type — This is a number that determines on what day the week
begins. The default is 1. If return_typeis 1 or omitted, the week begins
on Sunday. If return_typeis 2, the week begins on Monday. re-
turn_types of 11 through 17 are new in Excel 2013 and specify that the
week should start on Monday (11) through Sunday (17). The new re-
turn_typeof 21 ensures that every week has exactly 7 days. Weeks
always start on Monday, but the first Thursday of the year is the
middle of Week 1.
The ISOWEEKNUM function is the same as using a return_typeof 21 in the
WEEKNUM function. ISOWEEKNUM is new in Excel 2013. It returns a #NAME?
error in previous versions of Excel.
Figure 11.43 compares ISOWEEKNUM to WEEKNUM. Notice that the outlined
Week 1 in columns B:E is always 7 days in duration.