Week number of a quarter - excel

Question

I'm trying to get the week number of a given quarter based on the date.
I currently have this formula
=1+(WEEKNUM(EDATE(Y4,-1)))-(WEEKNUM(DATE(YEAR(EDATE(Y4,-1)),
LOOKUP(MONTH(EDATE(Y4,-1)),{1,4,7,10}),1)))
But for January, it should be giving me 1 but it's giving me 10. Any suggestions?

Answer 1

How do you expect this to work at the start and end of the quarter? Default WEEKNUM function starts week 1 on the 1st of January every year and week 2 starts on the next Sunday after 1st January.
Assuming your quarter week numbers should work the same way, i.e. week 1 starts on the 1st of Jan/Apr/Jul/Oct and week 2 starts on the next Sunday then that's actually equivalent to counting Sundays since 6 days back into the previous quarter.
You can do that using NETWORKDAYS.INTL function, i.e. with this formula:
=NETWORKDAYS.INTL(EOMONTH(Y4,MOD(1-MONTH(Y4),-3)-1)-5,Y4,"1111110")
format result as number with no decimal places
NETWORKDAYS.INTL function is available in Excel 2010 and later versions - for older versions of Excel you can get the same results with this formula:
=INT((13-WEEKDAY(Y4)+Y4-EOMONTH(Y4,MOD(1-MONTH(Y4),-3)-1))/7)

Answer 2

(Expanded from comment)
when you choose a date in January, it's going back to December. 12 in your lookup array gives 10 as the result. Perhaps instead of EDATE, you should use EOMONTH(Y4,-1)+1, so you look at the 1st of the current month for your calculation
=1+(WEEKNUM(EOMONTH(Y4,-1)+1))-(WEEKNUM(DATE(YEAR(EOMONTH(Y4,-1)+1), LOOKUP(MONTH(EOMONTH(Y4,-1)+1),{1,4,7,10}),1)))

Answer 3

This is fairly interesting, since it changes with the year, and changes with what day of the week is the "start" of the week. So if a quarter starts on Saturday, and the week starts on a Saturday, the entire week is week 1. However, if it starts on a Sunday, week 1 is only one day long, and week 2 starts on Sunday.
The first question we have is, what day is it?
=DayCheck
Additionally, I'm going to call the start of each quarter the following:
Q1Start = Date(Year(DayCheck),1,1)
Q2Start = Date(Year(DayCheck),4,1)
Q3Start = Date(Year(DayCheck),7,1)
Q4Start = Date(Year(DayCheck),10,1)
The next question is, what's the first day of the week? We have some control over this with the Weekday function. For the sake of keeping it simple, Sunday is the start of the week.
Ok, that's our day. Next, what quarter is it?
`Quarter=ROUNDDOWN(MONTH(O16)/4,0)+1`
This gives us 1 for Q1, 2 for Q2, etc.
What day of the week is it now?
=WEEKDAY(DayCheck,1)
Ok, and now, what week are we on?
=WEEKNUM(DayCheck,1)
I'm going to put it together in a not very elegant fashion. I'm sure there's a better way out there.
=(Quarter=1)*((Weeknum(DayCheck)-WeekNum(Q1Start)+1)+(Quarter=2)*((Weeknum(DayCheck)-WeekNum(Q2Start)+1)+(Quarter=3)*((Weeknum(DayCheck)-WeekNum(Q3Start)+1)+(Quarter=4)*((Weeknum(DayCheck)-WeekNum(Q4Start)+1)

Answer 4

Try this:
=CHOOSE((MOD(WEEKNUM(Y4),13)=0)+1,WEEKNUM(Y4)-(ROUNDDOWN(WEEKNUM(Y4)/13,0)*13),13)
This will get the week number of a given date within a quarter.
I used this in one of my applications so you might be able to use it too. HTH.
Note: If you use 1st day other than Sunday, then adjust the WEEKNUM formula.

Answer 5

Can try this as I got this as combination of 2 formula
=WEEKNUM(A1,1)-(INT((MONTH(A1)-1)/3)*13)
second part - INT((MONTH(A1)-1)/3) gives us the quarter number of previous quarter which then multiplied with 13 weeks/quarter gives us how many weeks have passed in all previous quarter before current quarter.
First part - "WEEKNUM(A1,1)" gives us the week number of current week in the year.
so by deducting all the previous weeks in previous quarters from current week number of year, we get the current week number in current quarter.