This is calculated by claymore as I said in first post its an estimate value it depend on how fast your cpu clock cycles are thats how claymore does it I think. My program read memory inside claymore miner and look for dev fee wallet on certain positions and compare it with your wallet in config. If it doesn't match your or my wallet then claymore changed it because its about to mine next fee. Based on how many times it change I calculate the time 1 change should happen about once per hour +- few minutes/seconds based on how many cpu cycles are used. I think if you just set your miner process priority to Idle it will mine fee every 1h2min instead of 1h. (again these are not actuall values but it should work this way) it definetly doesn't calculate it from date it uses cpu clock ticks since start of your miner. My program keeps the amount of fees mined stored in memory so if you mine for 5 days you should get 9/10 fees mined and if your miner crashes it will be automatically restarted and you will still continue to mine at 9/10 it will not reset to 4/5. And the saved time shown in console is simply calculated by (amount of fees saved * 36 or 72 seconds. )