If a resource's hire date is mid time period, they are able to enter time on the Classic timesheet for that time period even if it's prior to their hire date in Classic Clarity.
Steps to Reproduce
Expected results: Resource cannot enter time for the 21st and 22nd September 2020
Actual results: The time can be entered for the days in the week prior to the date of hire.
Release : All Supported
Component : CA PPM TIME MANAGEMENT
This is working as designed in Classic Clarity. The product does not exclude the days prior to the Hire Date that are part of an open time period (the whole time period that matches the hire date will be allowed for posting)
This functionality is available in Modern User Experience starting in 15.7 (added as part of DE49901/DE49826), so the recommendation is to use the Modern User Experience for timesheets.
Note: In Classic, there might be a possibility of achieving this behavior with an automated process, similar to the discussion in this Communities thread:
Prevent Time Tracking to Project / Tasks closed for time entry?
That option would be outside the scope of Support though, as this would be a customization.
See New UX Timesheets able to be created Prior to 'Hire Date' for a defect fixed in 15.7