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

Note
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.

Note
Constraints on Boolean expressions are described in the topic, CALCULATE Function.

When the current context is a single date, the date returned by the FIRSTDATE and LASTDATE functions will be equal.

Technically, the return value is a table that contains a single column and single value. Therefore, this function can be used as an argument to any function that requires a table in its arguments. Also, the returned value can be used whenever a date value is required.

This DAX function is not supported for use in DirectQuery mode. For more information about limitations in DirectQuery models, see  http://go.microsoft.com/fwlink/?LinkId=219172.

The following sample formula creates a measure that obtains the first date when a sale was made in the Internet sales channel for the current context.

To see how this works, create a PivotTable and add the field CalendarYear to the Row Labels area of the PivotTable. Then add a measure, named FirstSaleDate, using the formula defined in the code section, to the Values area of the PivotTable.

=FIRSTDATE('InternetSales_USD'[SaleDateKey])

Reference

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