Time
Time is a factor in The Grand Theft Auto Universe. It moves at a rate of 1 second in real time is 1 minute ingame, making 1 ingame hour a minute and 1 ingame day 24 real time minutes. Time is in military time in the game, starting a 00:00 and going to 24:59 at midnight.
In the games, espeically in Grand Theft Auto: San Andreas, the day-and-night cycles along with the weather moves along with the time.