This will let you choose from either; 1930, 40, 50, 60, 70, 80, 90 and 2000 at the start of Sandbox mode.
1. Click 'Start' and then 'Run'
2. Type in 'regedit' (just the text)
3. Click on the names in this order; HKEY_CURRENT_USER\Software\Lionhead Studios Ltd\TheMovies
4. Once you've gone to 'The Movies', double click on 'Allow Any Decade'
5. In the 'Value Data' box, change the '0' to a '1' and then press 'OK'
6. Close the window, start 'The Movies' and enjoy
BTW, don't screw around in the Regestry Editor because it can screw up different things