This happens if the system's internal clock is reset. If it happens again, it is possible that your internal battery might be failing, which would be a quick repair at your local dealer (the battery is meant to outlast the computer, by design, but this isn't always the case).
To set the date and time, open the Date & Time pane in System Preferences.
As for your question about getting out of the seventies, try these steps:
- Cut your hair.
- Learn to be cynical.
- Replace your record player with an iPod. Replace the "evil" independent punk/rock/motown music with more sophisticated corporate produced bands.
- Forget how to disco.
- Replace harmful, illegal drugs like marijuana with "safe" legal equivalents like tobacco and alcohol.
- Bury your paisley shirts, and ...
- Sell your platform shoes and gold chains.
Only kidding!
"I never could get the hang of Thursdays."
- Hitchhikers Guide to the Galaxy, Douglas Adams.