Date Forumla

This is because in your first example it is being evaulated as a column where as in the second it is a measure.

In a column you can use another column in the formula without aggregating due to the row context. Measures do not have row context so you will need to aggregate the columns. Which aggregation you should use depends on the model.

Hi , 

As indicated in the error, you are creating a measure instead of a column , measure's work on aggregated format, where as columns work on row level. This is the reason for your error indicated.

Regards.