Here is a 42-year-old version of the longtime television judge looking ready for the cameras at an event at the Hard Rock in London back in 2001 (left).

And, 18 years later ... the 59-year-old father of one who is now one of four judges on the long-running "America's Got Talent" ... which just wrapped its 14th season of the performance-based program ... showing off his golden buzzer worthy looks at the season finale of the talent show in Hollywood last month (right).

Cowell turns the big 6-0 Monday ... bloody brilliant!

The question is ...