STARTOFMONTH Function (DAX)
Returns the first date of the month in the current context for the specified column of dates.
To understand more about how context affects the results of formulas, see Context in DAX Formulas.
The dates argument can be any of the following:
A reference to a date/time column.
A table expression that returns a single column of date/time values.
A Boolean expression that defines a single-column table of date/time values.
Constraints on Boolean expressions are described in the topic, CALCULATE Function (DAX).
The following sample formula creates a measure that returns the start of the month, for the current context.
To see how this works, create a PivotTable and add the fields CalendarYear and MonthNumberOfYear to the Row Labels area of the PivotTable. Then add a measure, named StartOfMonth, using the formula defined in the code section, to the Values area of the PivotTable.