The question is what result you actually want as you don't say.
The proper function would likely be the INTNX function.
Result= intnx('quarter', datevariable,0,'B') would provide the first day (begining) of the calendar quarter the date occurs in.
Result= intnx('quarter',datevaraible,0,'E') would provide the last day (end) of the calendar quarter the date occurs in.
Result = intnx('quarter',datevaraible, 1,'B') would provide the first day of the next calendar quarter. I think this might be the one you want but provided the others just in case.
If your variable is actually a datetime you would use DTQUARTER instead. It is amazing how many people do not differentiate between "date" and "datetime" values.
Reason to use INTNX is that it will account for possibly issues with leap days.
And the companion function INTCK returns number of intervals between to dates, time or datetime values.