yes, do as following to adding an hour to the current EPOCH (Using GNU date):
date -d'+1hour' +%s%3N
or adding an hour and 10 minutes and 20seconds
date -d'+1hour +10minutes +20seconds' +%s%3N
or add all in seconds (1hour+10min+20sec=4220sec):
date -d'+4220seconds' +%s%3N