The history/timeline of Hinduism would be a very interesting topic. As one researches more and more, more and more things keep coming. Yes, there are many sources that indicate many of the historic milestones seen by Hinduism, but is there a recorded history available ? As we see Hinduism is knowledge and experience supported religion, the ancestors have well thought of the need to record some of the important moments in the history. This history is given to us in the form of purANas and itihAsas. The word purANa means old and itihAsa means history. They refer to events that are very many thousands years old.
The history told in these purANas and itihAsas has the information as to who were the key people lived in various points of time - especially the sages and the kings and remarkable achievements by them if any. These texts apart from providing the mere information also serve as the source that inspires people about the heroes of the past. They narrate the good and evil of the past so that people could take forward the contours of positive growth and keep away from the errors.
The purANas are eighteen in count. There are also an equal number of sub purANas. (upa-purANas). They talk of the happenings of very ancient time. These typically in terms of many yugas (multi thousands years), chaturyugas (four such yugas is one chaturyuga), manvantara and kalpa. It would be quite involved task and at times impossible to assign a fixed date for these happenings. purANas came through various sources and were compiled by sage vedavyAsa. The importance that is given to the history and these purANas in Hinduism is obvious by the fact that some part of the purANas is read out as part of the daily worship in the temples along with the vedas. The knowledge of this ancient past was spread mainly through the word of mouth through the channels called paurANikas. So apart from the original theme, many later day insertions also could be found in them.
Medival History of Hinduism
itihaas are the narration of incidents at two moments in this chaturyuga. There are two in number. One is rAmAyaNa written by vAlmIki and the other is mahA bhArata written by vedavyAsa. Of these rAmAyaNa narrates the story of the earlier time (tretAyuga) and mahAbhArata the incidents of later time (dvAparayuga). (The currently running yuga is kaliyuga). Though they talk elaborately about a war each, the precursor to the war and the scenario after that, they give account of the previous kings who ruled and their deeds. The later epic mahabharata tells the post war history upto the start of the current yuga - kali. How scientifically are these data captured ? Hindus, who are well known for their astronomy through olden times, have marked the celestial positions of the planets as a way of presenting the time. By decoding these one could get the period.
Modern History of Hinduism
The recent periods of Hinduism (after 1st century ACE) though did not have a single consolidated documented history. However, the histories of many of the glorious personalities were well written. There are numerous such biographies that talk about the social, political setup during those periods. Apart from these the kings had the inscriptions made on stones and copper plates (epigraphs) that briefly tell about any special event like construction of temples etc that happened during the reign of a king. These clearly mention the year in which the event happened. Given the robustness of these materials they stand well for very many centuries. So these serve as the historic evidences and help determining the dates of other contemporaries using the references mentioned in them.
The 2nd millennium was a dark period when the land in which Hinduism was glittering gloriously, that India was attacked by the Muslim invaders. (The European take over subsequently was a boon and a bane in that time period.) Much of the well-matured culture was put into shambles and much of the glory forgotten. The vibrant open discipline, which was highly advanced spiritually and philosophically in the peaceful past had to defend itself against the continuous wave of attacks. As this period was really too long many of the Hindus on the forefront had to shelve the knowledge ocean of the past and just pick some simple abstracts out of them to survive as Hindus even in the hostile environment.
At the end of the 2nd millennium efforts started to collect the records of the glorious past of Hinduism whatever were remaining. These form the basis of the modern history of Hinduism.
The sanAtana dharma (eternal discipline) through its journey has seen at one point a religion that was spread throughout the world to get confined to the land of Indian subcontinent and even there it had glorious as well as troublesome periods. May the Supreme bless now for the benefit of the humanity that the great truths of this dharma becomes available in its pure form to all the seekers throughout the world.