Source : Free On-Line Dictionary of Computing

time shifting
     
         A technique used to work around problems due to
        the {Year 2000} and the "millennium bug".  Time shifting
        involves translating date fields in a database back by a fixed
        number of years to avoid year 2000 problems with the {database
        management system}.
     
        Typically dates are shifted back 28 years so that the occurrence
        of leap years and days of the week match with the actual year.
     
        (2003-08-15)