Hi Triven,
Please find below clarification:
Time Evaluation Dates - 26th to 25th of every month
Payroll Dates - 1st to 30th or 31st of every month
when you process payroll for any month you run the time evaluation for Previous month 26th to current month 25th.
Lets assume that you are processing the payroll for the month of Dec'14 for the employee who is doing night shift, you run the time evaluation till 25th Dec and system assumes the employee is present for the balance 6 days and pays the night shift allowance till 31st Dec. Now, You have changed the shift of the employee to Day Shift w.e.f 01.01.2015 and when you process the January payroll (Time Evaluation from 26th Dec - 25th Jan'14) system checks for the payment made for the 6 days of Dec'14 which you have already processed, system process the salary for the day shift allowance from Jan'14.
If you have changed the w.e.f date of Day shift to 26th of Dec'14 and run the time evaluation, system will process the difference amount (For 6 days Night Allowance which was paid extra in Dec payroll) will be adjusted in Jan'15.
For this you just have to write a PCR for Night allowance and the standard time configuration. Don't have to do any specific configuration.
Regards
Ravi