- A part of the Jewish Calendar. Ab is in the complicated Jewish Calendar.
- A blood type. The Doctor said, "you have AB blood".
The Jewish CalendarEdit
The Jewish Calendar is not the normal Western Calendar, which is Gregorian. The Jewish Calendar is quite unusual, but very clever. It is based on the fact that the rotation of the Earth takes one day, that the moon orbits (goes round) the Earth in a month and that the Earth orbits the Sun every year. This, however, is slightly wrong because there are a few hours difference - it isn't much, but they build up after a little while. It is why the Gregorian Calendar has leap years. The Jewish Calendar is very complicated to work out for anyone: a bit more information can be found here, however.