Issue:

Let’s say User's ‘Vacation’ time off have the following settings:
Effective Date: Jan 1-2010
Balance: Set to 10 days
Accrue: By 1.25 days Monthly 15th of the Month.
Reset: No reset
Limits: No Limits

When you run ‘Time off History’ report for the User for the time off ‘Vacation’ with the date range selected from ‘Jan 1, 2010-Dec 31, 2010’, it should show ‘new policy start day’ as Jan 1, 2010 instead it shows some other date.

Cause:
This is most likely happen when the ‘Vacation time off’ policy's effective date was set before the user’s start date, defined in his profile. 
When the time off policy effective date is set before the user’s start date then the report will always pick up the user’s start date defined in his profile as the time off policy’s effective date.

Solution:
Change the Time Off policy’s effective date to be on or after the user’s start date, defined in the user’s profile in order for report to show the same date.