FIRSTDATE DAX Function (Time Intelligence) Context Transition

Returns first non blank date.

Syntax

FIRSTDATE ( <Dates> )

Parameter	Attributes	Description
Dates		The name of a column containing dates or a one column table containing dates.

Table A table with a single column.

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.

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
- CALCULATETABLE ( DISTINCT ( <Dates> ) )
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.

The result table includes only dates that exist in the dates column.

The function MIN should be used instead of FIRSTDATE when the result must be a scalar value instead of a table.

Learn more about FIRSTDATE in the following articles:

Semi-Additive Measures in DAX

Values such as inventory and balance account, usually calculated from a snapshot table, require the use of semi-additive measures. In Multidimensional you have specific aggregation types, like LastChild and LastNonEmpty. In PowerPivot and Tabular you use DAX, which is flexible enough to implement any calculation, as described in this article. » Read more
Understanding the difference between LASTDATE and MAX in DAX

This article explains why in many cases, MAX should be used instead of LASTDATE to search for the last date in a time period using DAX. » Read more

Other related functions are:

Contributors: Alberto Ferrari, Marco Russo