Age Manipulation (others) – The ability to age others. Subareas include the ability to make another person younger, older and/or negate their aging.
Halflife (Marvel) can make people older.
Time Master (Marvel) was aging people back in the sixties in Tales to Astonish #63.
Age Manipulation was a common DC Silver Age plot gimmick. Batman V1 #119, Flash V1 #157, Jimmy Olsen V1 #66, and Lois Lane V1 #40 have stories about accelerated aging.
Superman wins the prize for being made older (Action Comics V1 #251, Action Comics V1 #270, Action Comics V1 #396).
Supergirl (DC) is turned into adult due to Red Kryptonite and cannot join the Legion of Superheroes in Action Comics V1 #267.
The Silver Age also abounded with stories of characters made younger via one plot device or another (Adventure Comics V1 #317, Batman V1 #147, Jimmy Olsen V1 #66, Adventure Comics V1 #356, Lois Lane V1 #10, Action Comics V1 #284).
Alpha the Ultimate Mutant (Marvel) Defenders V1 #16
Jetta of the 21st Century #7 (Standard)
Professor Enigma (Fantagraphics) Love and Rockets V4 #3
Kaine Salinger (DC) – Outcasts #1
Jimmy Olsen (DC) fools around with an age accelerator in Superman’s Pal #85 with unfortunate results.
Jimmy Olsen (DC) becomes a baby in Superman’s Pal #54.