Chronos' Timer is a Black Market item worth 2 passes. Chronos' Timer enables your horses to make progress twice as fast, and therefore complete their training at a young age.
Riding, training and learning through competitions are the activities affected by Chronos' Timer.
Be aware that Chronos' Timer will not double the skills your horse can acquire. It will only enable its learning speed to double.
When used with Water Of Youth, the Chronos Timer will still work, but is effectively cancelled out. It will take the same amount of effort to produce the same results, but the horse will only be half the age.
Name after the Greek Titan Chronos