September, 1999 - They talk about PoH & PoSky porting spells existing prior to September 1999.
October, 1999 - Sol Ro Released.
Other fun tid bit.
May, 2000 - "Increased the number of frightfingers in the Plane of Fear. Previously only 3 frightfingers would pop per respawn. "
I didn't play classic classic classic. So I don't know if Allakhazam notes are to be trusted. But hey, seems like PoSky/PoHate come out before Sol Ro right? (what I was really looking for was the date LR was removed, because i'm 99% sure when it was removed, class gear was introduced...)