STARTOFMONTH DAX Function (Time Intelligence)  Context Transition

Returns the start of month.

Syntax

STARTOFMONTH ( <Dates> )
Parameter Attributes Description
Dates

The name of a column containing dates or a one column table containing dates.

Return values

Table A table with a single column.

A table containing a single column and single row with a date value.

Notes

In order to use any time intelligence calculation, you need a well-formed date table. The Date table must satisfy the following requirements:

  • All dates need to be present for the years required. The Date table must always start on January 1 and end on December 31, including all the days in this range. If the report only references fiscal years, then the date table must include all the dates from the first to the last day of a fiscal year. For example, if the fiscal year 2008 starts on July 1, 2007, then the Date table must include all the days from July 1, 2007 to June 30, 2008.
  • There needs to be a column with a DateTime or Date data type containing unique values. This column is usually called Date. Even though the Date column is often used to define relationships with other tables, this is not required. Still, the Date column must contain unique values and should be referenced by the Mark as Date Table feature. In case the column also contains a time part, no time should be used – for example, the time should always be 12:00 am.
  • The Date table must be marked as a date table in the model, in case the relationship between the Date table and any other table is not based on the Date.

Remarks

The <Dates> argument can be any of the following:

  • A reference to a date/time column. Only in this case a context transition applies because the column reference is replaced by
  • 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.

STARTOFMONTH filters <Dates> into a 1-row, 1-column table that shows only the earliest date, in the entire <Dates> column devoid of all filters, that is in the same year and month as the earliest visible date in <Dates>.

The following STARTOFMONTH call

STARTOFMONTH ( 'Date'[date] )

is a more efficient implementation of the following semantically equivalent expression:

VAR FirstDateVisible =
    CALCULATE ( MIN ( 'Date'[Date] ) )
VAR FirstYearVisible =
    YEAR ( FirstDateVisible )
VAR FirstMonthVisible =
    MONTH ( FirstDateVisible )
VAR DaysInMonth =
    FILTER (
        ALL ( 'Date'[Date] ),
        YEAR ( 'Date'[Date] ) = FirstYearVisible
            && MONTH ( 'Date'[Date] ) = FirstMonthVisible
    )
VAR FirstDayInMonth =
    MINX (
        DaysInMonth,
        'Date'[Date]
    )
VAR Result =
    CALCULATETABLE (
        VALUES ( 'Date'[Date] ),
        'Date'[Date] = FirstDayInMonth
    )
RETURN
    Result

Related articles

Learn more about STARTOFMONTH in the following articles:

  • Semi-Additive Measures in DAX

    Values such as inventory and account balance, usually calculated from a snapshot table, require the use of semi-additive measures. This article describes how to implement these calculations in DAX according to your specific requirements. » Read more

Related functions

Other related functions are:

Last update: Nov 20, 2020   » Contribute   » Show contributors

Contributors: Alberto Ferrari, Marco Russo, Jes Hansen

MSDN documentation: https://docs.microsoft.com/en-us/dax/startofmonth-function-dax

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Context Transition

This function performs a Context Transition if called in a Row Context. Click to read more.

Row Context

This expression is executed in a Row Context. Click to read more.

Iterator

Not recommended

The use of this function is not recommended. See Remarks and Related functions for alternatives.

Not recommended

The use of this parameter is not recommended.

Deprecated

This function is deprecated. Jump to the Alternatives section to see the function to use.

Deprecated

This parameter is deprecated and its use is not recommended.

DirectQuery compatibility

Limitations are placed on DAX expressions allowed in measures and calculated columns.
The state below shows the DirectQuery compatibility of the DAX function.

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