How far back does History go?

I use Safari on my iPhone, but always another browser on my iMac.

I just opened Safari on my iMac and looked at my History: I had no idea that the History was synced and recorded from my iPhone! This is really great and helpful.

However, I noticed that the entries start on 24 September which seems quite a random date.

I'm just scratching my head trying to figure out why on 24 September it decided to start recording my History. Might I have unknowingly changed a setting in iCloud on that date to start recording/syncing the History?

Any help or insight would be appreciated.