Real time within Spiral Knights is measured relative to Three Rings' time zone, which is always the local time in San Francisco, California, USA. The current game time can always be checked by going to the Arcade, inspecting any active gate, and looking at the top of the gate window.
Because California observes daylight saving time, game time varies with respect to GMT throughout the year. Game time is GMT-8 in the winter months (from the first Sunday of November to the second Sunday of March). Game time is GMT-7 in the summer months (second Sunday in March to first Sunday in November).
Every morning at 5:00, the game servers reboot. Every second evening at 20:00, the gates in the Arcade cycle.