The story starts in the year 1041, in the Imperial Calendar, of the nation it's set in. The empire in question hasn't actually been around that long -- only about 400 years -- but the calendar was created about 50 years into the empire and used the reign of a famous, possibly mythical, king in the nation's past to act as the origin date. The idea is that this legendary king's reign marked the beginning of the nation's ascension that has culminated into the modern empire.
In the year 1041 IC, narrator and lead character Gideon Fane is 25 years old. He's considered somewhat old for a bachelor, and will remain one all his life, though he comes close to proposal and marriage once (which may be removed or change to more than just once over the course of writing). His friend Michael Donovan is 26, and has been married to Angela Silverstein (24 years old) for seven years.
Gideon has known something of how to do magic for six years now, but he first learned he had the aptitude when he was 15. He was forbidden to learn it until his father died and could no longer take him out of the will (his mother had been dead since Gideon was 9, and he had no siblings). Gideon went and learned how to do magic immediately, even though it was considered improper for a gentleman to do magic.
The novel is intended to span over about 25 years, though obviously there will be gaps of time. It ends in 1066 IC, when Gideon is about 50 years old. Society will have gone through what Gideon considers a marked decline in that time, which contributes somewhat to his final decision to go through with the transformation.