Aidan of the tavern
Auror
I also make a table/chart with the year of various characters' births and major life events. It's a good time-chart to figure out how old characters are in relation to each other (etc) throughout the story, and how old they were when certain major events happened. For example, a new King is crowned, there is a war, etc. This is particularly useful if the characters are related (not just by blood but by circumstance). Few authors mention exact ages I've noticed, but it's helpful to know what the rough ages are, so that I don't accidentally make the King 90 years old or something.
This can also help plot snarls that may crop up.
Yes, I have a timeline which I fill in to give me an idea of the timeframe. Otherwise I get confused and contradict myself. I also make a note of character ages even though I probably won't tell the reader .