The pilot reported that, during a night flight, in his tailwheel ski-equipped airplane, weather conditions began to deteriorate, and he elected to navigate to a nearby airport, with an estimated 20-minute fuel reserve upon his arrival. Once at the intended airport, he was unable to activate the runway lights via the pilot-controlled lighting and diverted to an alternate airport approximately 35 miles away. About 10 nautical miles from the alternate airport, the engine lost all power due to fuel exhaustion. Subsequently, he made an emergency landing to an off-airport field. During the emergency landing the ski-equipped airplane nosed over and sustained substantial damage to the empennage. 14 Code of Federal Regulation 91.151 Fuel requirements for flight in VFR conditions, states in part: (a) No person may begin a flight in an airplane under VFR conditions unless (considering wind and forecast weather conditions) there is enough fuel to fly to the first point of intended landing and, assuming normal cruising speed- (1) During the day, to fly after that for at least 30 minutes; or (2) At night, to fly after that for at least 45 minutes. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.