I need to do a subtraction between two dates

Summary:

I need to do a subtraction between two dates, to check if the action date is in a range of days.

Content (required):

I need to know if the action date that the line manager selected when subtracting with the start date , how many days the employee has in the company, with this number I validate with the reason he selected if it is within the possible.

Version (include the version you are using if applicable):

22B

Code snippet (add any code snippets that support your topic, if applicable):