1200z Time Explained

Military time notation is based on 24-hour clock. A time of day is written in the form hhmm, where hh (0-23) stands for full hours that have passed since midnight, mm (00-59) is the number of minutes that have passed since the last full hour. To convert hours greater then 12 to 12-hour clock just subtract 12 from the given hours and that will give you the PM time