2AM marks the ninth night hour of the planetary hour system, reckoned from the temporal hours the tradition actually uses rather than the fixed sixty minute clock hour a modern reader assumes by default. A temporal hour divides the interval from sunrise to sunset, or from sunset to the next sunrise, into twelve equal parts regardless of season, so a summer night hour and a winter night hour are different lengths in real minutes even though both count as one twelfth of the night span; only at the equinox, when day and night are equal, does the temporal hour match the clock hour closely enough to set a single fixed table like this one.
The system draws on only the seven planets visible to the naked eye, ordered by the Chaldean sequence of their apparent orbital speed as seen from earth, Saturn slowest, then Jupiter, Mars, the Sun, Venus, Mercury, and the Moon fastest, and that sequence repeats continuously through both the twelve day hours and the twelve night hours. Because a full day runs twenty four hours and the sequence repeats every seven, the ruling planet of a day's first hour shifts forward from one day to the next in a fixed order, and it is that first hour planet which actually names the day of the week: Sunday for the Sun, Monday for the Moon, Tuesday for Mars, Wednesday for Mercury, Thursday for Jupiter, Friday for Venus and Saturday for Saturn. On a Sunday, by that reckoning, 2AM falls to Mars, the ninth hour of the night.