This feature is currently for EQ1. You can bring up the Spell Timer by pressing on the Main Control. This window automatically shows timers for any spell cast on you. This includes your own buffs, buffs from others, bard songs, and detrimental spells.
You can resize the Spell Timer window any way you like.
The Spell Timer will warn you when your buffs are about to fade. You can enable or disable this feature with the checkbox "Spells and buffs ending soon" on the Alert Options.