The Time of Troubles occurred in 1358 Dalereckoning, the Year of Shadows. Ao, the overgod, cast the gods down in mortal form among the peoples of Faerûn, to find the Tablets of Fate that had been stolen. The thieves were the Dead Three, Bane, Bhaal and Myrkul, who all died during the Time. Other occurrences during the Time of Troubles were a rules shift from first edition AD&D to second, arcane magic going awry and divine magic not working, and generally bad writing.
I've noticed a couple of FR threads from you and thought I should recommend that you go to www.candlekeep.com if you have any more FR questions. There are a lot of FR experts there, including various authors.