Date.StartOfQuarter Function in Power Query

The Date.StartOfQuarter function in Power Query (M language) returns the first day of the quarter for a given date, datetime, or datetimezone value, with the time component set to midnight (00:00:00).

Syntax

Date.StartOfQuarter(
    dateTime as any
) as any

The function has the following parameter:

• dateTime: A value of type date, datetime, or datetimezone for which you want the start of the quarter.

Return Value

• Returns a value of the same type (date, datetime, or datetimezone) representing the first day of the quarter, with time reset to 00:00:00.
• Preserves the time zone if the input is datetimezone.

Quarter Calculation

• Q1 → January 1
• Q2 → April 1
• Q3 → July 1
• Q4 → October 1

Example: With a datetime.

Power Query M

let
    Source = Date.StartOfQuarter(#datetime(2025, 8, 24, 15, 30, 45))
in
    Source   

The output of the above code is:
#datetime(2025, 7, 1, 0, 0, 0)

(Because 24-Aug falls in Q3, which starts on July 1.)

Example: With a date.

Power Query M

let
    Source = Date.StartOfQuarter(#date(2025, 2, 10))
in
    Source  

The output of the above code is:
#date(2025, 1, 1)

Example: With datetimezone.

Power Query M

let
    Source = Date.StartOfQuarter(#datetimezone(2025, 10, 15, 12, 0, 0, 05, 30))
in
    Source    

The output of the above code is:
#datetimezone(2025, 10, 1, 0, 0, 0, 05, 30)