month-year data type week number determination

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Imported from previous forum

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Hi,

In FIX 4.4 the month-year data type specifies a possible format as YYYYMMWW where WW = w1, w2, w3, w4, w5.

How is the actual week number in the month determined?

The ISO 8601 standard has guidelines on how to determine if the first week in a year is the first week of this year or the last week of the previous year. It specifies that the first week of the year is the first week with the majority (four or more) of its days in the starting year.

Does the same rule apply in determining the week number for a particular week in a month?

For example, October '09 has only 3 days in the first week, which would put October 2nd in the last week of September, ie. the correct month-year for the week containing Oct 2 will be: 200909w5?

Similarly, the month-year value for the week containing October 9 will be 200910w1?

Is this how the week number determined when specifying a month year value in the format YYYYMMWW?
If not, what’s the correct way to figure out the week number…

Thanks in advance,
Anshul