I assumed it was the days "listed" in the Razor Project Plan.pdf > Mining Advantage, in the graph with block reward, block height, coins minted and days @ rate.
A.K.A. I assumed + 87 days since launch, and reading that PoS starts 90 days after launch I didn't pay more attention, but maybe I'm wrong and you do have to add up the days instead? It does say at a point you'll eventually have 3 ways of "getting coins": "non-miners via Proof-of-Stake, large miners via the IMM, and smaller miners via the reduced Proof-of-Work rewards and transaction fees."