The Time of Bondsmen was unconditionally set to trigger around 240 BC since we felt that most players would be stuck with Freemen units for far too long otherwise.
The Time of Soldiers is the 3rd (and final) Celtic Era and I kinda doubt the idea that it occurs around 240 BC in general. Indeed: I myself play as the AS and now in 230-ish BC the Celts are still Bondsmen.