What date format do I need to use in order to calculate the days between one date and another?

Summary

What date format do I need to use in order to calculate the days between one date and another?

Content

Hello

I am busy creating a data model for a BI report. In the data model I want to calculate the number of days between the Termination Date and the Hire Date. But I only want to use the Month and Date for the calculation. For example, employee x has a Hire Date of 1990-01-24 and a Termination Date of 2021-03-31. Now I want to calculate the number of days between the month and date of the Hire Date (01-24) and the month and date of Termination Date( 03-31). The result should be 67 days between 24-Jan and 31-Mar. My problem is that the