Grin makes a better claim to the term timechain, because its emission is 1 Grin per second forever, literally keeping track of time. Beyond that, its difficulty

Grin makes a better claim to the term timechain, because its emission is 1 Grin per second forever, literally keeping track of time. Beyond that, its difficulty adjustment at every block keeps its average blocktime much closer to 1 minute than the once-every-2-weeks adjustment Bitcoin makes to try keep its average block time at 10 minutes.