You mint every 20 days. So you have 13 more to go.
Correct me if I'm wrong, but I don't believe that's accurate unless he received all of his coins in one block.
Suppose you were mining mint, and received 50k mint per day, in single lump sum payouts (1 payout per day) from a mining pool, from March 1st - March 3rd.
3/21 - the 50k coins you mined on 3/1 should now begin attempting to mint. Assuming they do mint today, in 20 days they will attempt to mint again.
3/22 - the 50k coins you mined on 3/2 should now begin attempting to mint. Assuming they do mint today, in 20 days they will attempt to mint again.
3/23 - the 50k coins you mined on 3/3 should now begin attempting to mint. Assuming they do mint today, in 20 days they will attempt to mint again.
Furthermore, depending on whether or not the minted coins become a part of the same block as the "chunk" of coins that they were minted from, you may end up with either 3 or 6 groups of coin ages in this example scenario, each of which would now be attempting to mint on different days.
Please anyone do correct me if I am wrong, but this is how hobonickels POS works and I believe Mint does it the same way.