Returns the first date of the month, quarter or year.
Use with CALCULATE to return revenue on the first day of the month, quarter or year.
StartofMonth_revenue = CALCULATE(SUM(TransactionData[Revenue]),STARTOFMONTH(CalenderDate[Date]))
StartofQuarter_revenue = CALCULATE(SUM(TransactionData[Revenue]),STARTOFQUARTER(CalenderDate[Date]))
StartofYear_revenue = CALCULATE(SUM(TransactionData[Revenue]),STARTOFYEAR(CalenderDate[Date]))