As you can see from our gallery below of Rock Stars Over 70 Years Old, time sure flies when you're having fun.

As hard as it is to believe, classic rock has been around for more than five decades now. That means the fresh-faced young upstarts who revolutionized the music world are now the wise elder veterans who set the standard younger generations will forever strive to match.

To commemorate the passing years, we've complied "then and now" photographs of each and every artist. In many cases, the hair has turned gray or retreated a bit. (Smart move by Brian Johnson to latch onto that newsboy hat so early in life, right?)

Their clothing tends to be a bit more conservative -- except for Iggy Pop, of course -- and the lines on each face are much clearer. But look at how the smiles, passion and intensity burns as brightly as ever after all those years. Long live rock!

Further Rock Star Birthday Reading:
Tom Petty Fans Celebrate His Birthday With a Vampire Walk
Wolfgang Van Halen Celebrates the 40th Birthday of 'Eruption'
Revisiting David Bowie's 50th Birthday Party
The Night Metallica Dressed Up as Lemmy
Sammy Hagar's Famous Friends Wish Him a Happy 70th
Lemmy's Star-Studded 70th Birthday Party
What to Get Rod Stewart for His Birthday? A Faces Reunion!
Top 10 Classic Rock Birthday Songs
Steven Tyler, Slash and John Fogerty Celebrate Howard Stern's Birthday
All Ringo Starr Wants for His Birthday Is Peace and Love