TITLE: Math equation/formula to get quarter based on custom fiscal year end
QUESTION [0 upvotes]: Given the calendar year end, which is Dec, we know that Quarter 1 is Jan - Mar, Quarter 2 is Apr - Jun, Quarter 3 is Jul - Sep and Quarter 4 is Oct - Dec.
My question is, is there a formula to get the correct quarter given the Year End (i.e. Apr Year End, Aug Year End, Dec Year End etc) and given the current month, it knows which quarter it'll be.
Below is the table of the quarters based on each month given it's year end.
\begin{array}{|c|c|c|c|}
\hline
& Dec\ (Year\ End) & Apr\ (Year\ End) & Aug\ (Year\ End)  \\ \hline
 Jan & Q1 & Q3 &Q2\\ \hline
 Feb  & Q1 & Q4 &Q2\\ \hline
 Mar  & Q1 & Q4 &Q3\\ \hline
 Apr & Q2 & Q4 &Q3\\ \hline
 May  & Q2 & Q1 &Q3\\ \hline
 Jun  & Q2 & Q1 &Q4\\ \hline
 Jul & Q3 & Q1 &Q4\\ \hline
 Aug  & Q3 & Q2 &Q4\\ \hline
 Sep  & Q3 & Q2 &Q1\\ \hline
 Oct  & Q4 & Q2 &Q1\\ \hline
 Nov & Q4 & Q3 &Q1\\ \hline
 Dec  & Q4 & Q3 &Q2\\ \hline
\end{array}
Please note that for Dec Year End, it means that Jan 1st is the start and Dec 31 is the end date.
Apr Year End, means that May 1 is the start and Apr 30th is the Year End.

REPLY [1 votes]: Let $x$ take the values $12,4,8$ when the years ends in Dec, Apr and Aug respectively.
Let $n=1,...,12$ index the months Jan,...,Dec.
Then the function $f(x,n)=1+floor[((n-1-x)mod12)/3]$ gives you the number of the quarter the month $n$ is in.
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