As far as I can think, Hinduism is a very old religion with many manuscripts reconstructed or timelines vague.
Discussing these timelines may become a matter of opinion rather than fact. Some sources may differ by a little amount whereas for some cases, there might not be any sources at all.
Keeping this in mind, let us take a look at an example:
How and when did astrology become a defining aspect of Hinduism?
There is no definitive answer to that question and I believe most answers will pick up from literary sources which may differ due to the sheer nature of this question.
So, are questions regarding timelines on-topic or not?