Finding the the beginning date for most date periods is simple. For example:
First day of this Year: Minimum (YearToDate)
First day of this month: Minimum (MonthToDate)
First day of Last month: Minimum (LastFullMonth)
First day of this week: Minimum (WeekToDate)

But there isn’t a comparably simple way to get the first day of the current calendar quarter. So if you ever need that calculation you can use the following formula:

Local numberVar x := Month (CurrentDate);
Date (
Year(CurrentDate), //Year
if x > 9 then 10 else
if x > 6 then 7 else
if x > 3 then 4 else 1, //Month
1 //Day
)

If you want the beginning of the quarter related to a field other than today’s date you can substitute a database field, formula or parameter in the two places that say “CurrentDate”.