Indeed, some users see the operating system return the correct date and conclude that all is well. It would be a big mistake to base operating system compliance on the ability of the date command to show a few selected dates correctly. Within an operating system such as HP-UX, critical functions such as file name and directory timestamps are handled by code paths different from the date command. And cron 's very critical functions are dependent on still other portions of the HP-UX code. Setting the date forward and then backward for testing is not a good idea with UNIX systems in general.
System files that end up with a future timestamp can cause some minor problems.
For Y2K application testing, it's a good idea to have a permanent system set to 2000 and port applications to this test bed. A few users have suggested running older systems 10 years in the past and then just adjusting a few date display programs to write the correct date. There will be a few glitches with this solution, especially if any data is to be shared with other systems. In this case, the system administrator will monitor the system every day, looking for errors. However, just like using the date command to see if the date rolls over, this approach is far too simplistic.