For reference, the "Haste" spell adds 15%
^ The above answer is semi correct.
There are limitations to the amount of haste gained from various sources: Equipment: 25% Includes Catastrophe Magical effects: ~43.75% Job abilities: 25% Haste gained from job abilities does not reduce spell recast timers
The maximum recast time reduction from all sources is capped at 50%, and the absolute maximum amount of haste from all sources is ~80%
Taken from the Haste (status effect) page on ffxiclopedia.org