The server is based in Germany and thus the server time is on German time. This is GMT+1 and 6 hours ahead of EST in the United States.
Sunrise happens at 6:00 server time and Sunset happens at 18:00 server time. (This works out to midnight and noon Eastern Standard Time. )
You "spend" time on almost every action you take during the game. Your time pool will gain 8 hours at every sunrise and sunset. It does not gain hours in real time. It never increases at any other time and can never contain more than 12 hours.