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In looking at each month, all months have different starting dates. Are there any rules and/or standards, out on the WWW, that helps in determining what is "the correct" Week Number one for any given month. Hum...
Any help would be greatly appreciated. Thanks,

What I have tried:

Implimenting my own definition of what is the months first week is. I'm looking for a more normal definition on the subject.
Posted
Updated 5-Jul-24 16:47pm

## Solution 1

ISO (in 8601 for instance) defines the first week of the year as the first week with more days in the new year than in the previous one.

I don't think I've ever heard of anyone determining the first week of a month, but I recommend following the same logic. So, the week which contains the fourth of the month, or the week which contains the first Thursday.

## Solution 2

I have not yet seen a specific standard that regulates the assignment of calendar weeks to months. ISO 8601 defines the calendar week on an annual basis, but not explicitly on a monthly basis. To ensure consistency, a week could be derived from the calendar week defined in ISO 8601:
- A week starts on Monday.
- The first week of the year is the week that contains the first Thursday of the year.

In practice, three methods could be used to assign weeks to months:

Majority principle:
The week is assigned to the month containing the majority of days in that week.

First day of the week:
The week is assigned to the month in which the first day of that week falls.

Last day of the week:
The week is assigned to the month in which the last day of that week falls.

I suspect that there may be slight differences in different countries.