Board Thread:Fun and Games/@comment-30736697-20170508230558/@comment-31063493-20170512175239

IIRC, it also says that the Z-Fighters are using the Hyperbolic Time Chamber to train.

So revive Cell, Throw him in the HTC for 8 hours. 8 hours = 4 months

It took Frieza 4 months to catch up to Goku and Vegeta.

Cell can likely train harder too because of his regeneration.