Midnight in military time notation is 0000 hours, often said as "zero hundred hours." The military uses this system of timekeeping because it reduces the chances of being misunderstood over the radio and in stressful situations, and it is easier to convert time between time zones.
Pronouncing military time is a little different. When speaking in whole hours, military time notation is said in hundreds. For example, 1200 is pronounced "twelve hundred hours." The time 0700 would be pronounced "oh seven hundred" or "zero seven hundred." When speaking in half hours, 1230 is "twelve hundred thirty hours." However, in order to pronounce a precise, non-even time, such as 1231, a military member simply recites the single digits: "one two three one."