Mixing MIN and ALL

Hello,

I'm working with a table containing a date column, and I want to get the oldest date in the table date column without being affected by the filters applied in the page.

If I create a measure "oldestdate = min(CCR_Consumption[usage_date])", syntax is OK but filters on the page will change the returned value.

If I use oldestdate = min(all(CCR_Consumption[usage_date])), I get an error message "The MIN function only accepts a column reference as an argument"

Thank you for your help.

Laurent