You must be riding any Saddlesore at some point during the Ides of a month. You may start the day before the Ides and finish on the Ides, or start on the Ides and finish the next day, or ride entirely on the day of the Ides.
Extensions Include:
12 Ides 1000
12 Ides 1000 Gold
12 Ides 1000 Insanity