Yanyu's notes on Astrology, and specifically how it intersects with history. (Now majorly corrected since the player was confused and didn't realize that this cycle of the Spider was the end cycle of the Spider in the Great Cycle of the Spider, not the first one.)
We are currently in the late cycle of the Spider in the third great cycle of the Dragon/Spider.
The Bear Emperors
The Bear Emperors lasted for 'over a century' with twelve Emperors. A great cycle is 169 years. I was suspicious, and it turns out that the Bear dynasty did last for about the length of a great cycle, but it turns out it wasn't an actual great cycle. It turns out that it started in the cycle of the Bear in one great cycle and ended in the cycle of the bear in the next great cycle, which is the next best thing to a great cycle. The last Dragon Emperor was about 650 years ago, and the first Bear Emperor was "two generations" after that.
The Great Cycle of the Phoenix started 663 years before the start of the current cycle. The cycle of the Bear in the great cycle of the Phoenix would have been 598 years before the start of the current cycle.
The Last Dragon Emperor
The last Dragon Emperor was roughly 650 years ago, according to the history. Exactly 650 years before the start of the current cycle was the start of the cycle of the Serpent in the great cycle of the Phoenix. The cycle of the Dragon (I'm using Dragon because it predated the spider replacing the dragon) in the great cycle of the Phoenix would have started 624 years before the start of the current cycle.
The Regency Council
The Regency Council has ruled for "seven generations". That would be 10 to 12 cycles ago. Twelve cycles ago would be the start of the current great cycle.