The basic cycle through which the whole cosmos passes is described as one day in the life of Brahmaa - that is one Kalp. It equals 4.320 million years, with a equally long night. One year of Brahmaa's life has 360 days and nights Thus this Universe is expected to last for 100 years of Brahmaa's life, who is currently believed to be 51 years old.

Rig Ved mentions 25 rivers in India.

How Saraswatee turned Brahmaa's head?
Brahmaa first created a woman from his body - Saraswatee, or Saavitree, or Gaayatree, or Brahmaanee. She was very beautiful. So when he saw his own creation he fell in love with her and started gazing at her. Saraswatee moved to his right to avoid his gaze, but a head immediately sprang up from the god's body. Now Saraswatee turned to the left and behind him, two new heads emerged. Then she darted towards Heaven, and a fifth head was formed. Brahmaa then said to his daughter, "Let us beget all kinds of living beings - men, Sur, A-Sur etc." Hearing this Saraswatee returned to Earth. Brahmaa wedded her and they retired to a secret place where they remained together for 100 Divine years.

(p 98)
As the Prince of Ayodhyaa, as the history and myth blend, Raam was probably a chief who lived in the 8th or 7th century BC - perhaps 300 years after king David ruled in Israel, and the start of Iron Age in central Europe, or about the same time as the Greeks began to develop city states. 

In the earliest stories about Raam, he was not regarded as Divine. Although he is now seen as an earlier incarnation of Vishnu than Krishn, he was added to the pantheon very late, probably after the Muslim invasions of the 12th century AD. His story became part of the cultures of Southeast Asia.
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(p 100) Shiv
O'Flaherty suggests that the worship of the Ling of Shiv can be traced back to the pre-Vaidik societies of the Indus Valley civilization (c 2000 BC), but that it first appears in Hindu iconography in the 2nd century BC. From that time a wide variety of myths appeared to explain the origin of Ling worship. The myths surrounding the origin of 12 Jyotirling (Ling of light) found at centers like Ujjain go back to the 2nd century BC, and were developed in order to explain and justify Ling worship.

(p 101) The Story of Ling Worship [This is a Pauraanik myth.]
Once in the past, when all the Universe had become a single ocean, Brahmaa, Vishnu and Rudra arose from the water. They were alone there at that time, even wise men did not know it. The Earth, which had been the domain of former beings, had been destroyed for a piercing wind had arisen and dried up the seven oceans. A single Sun appeared in the East and then a second one in the South, just like the first one, drying up all the waters with his rays and burning all that moved and was still. Then in the West a third Sun arose and in the North a fourth one; and later on eight more Suns arose, and thus there were 12 Suns.

Rudra, the Fire of the Doomsday, arose from the subterranean Hell and filled all the regions out of the sky. The exalted one, as he is known everywhere, burned all of the underworld above and sideways, without exception, and then he went to his dwelling place which he had built before. Then came clouds, rained flooding everywhere and all the regions of the sky with waters. Afterwards, they plunged into the single ocean. There was no earth, no sky, no space, no Heaven. Everything was like a giant cask filled up to the brim.

Then the three eternal Dev came out of the water. The two - Ka (Brahmaa) and Vishnu - bowed to Sarv (Shiv) who blazed with strong energy and said - "You are the Lord of everything, perform creation as you wish." "I will." He said. Then he plunged into the waters and remained immersed for 1,000 celestial years. Then they said to one another - "What will we do without him? How will creation take place?" Hari said to the creator - "Do as I tell you, O Grandfather, let no more time go waste, but make an effort to create progeny, for you are capable of creating various creatures. I will give you my own Shakti (power), so that you will be the creator." So he thought about creating and he creating everything conducive to happiness - Devtaa, Daitya, Gandharv, Yaksh, serpents, men.

When his creation was complete, Shambhoo came out of the water, desirous of creating and thinking about it in his mind. But when he saw the whole stretching above and below with the gods etc, the great Devtaa's heart filled with anger and he thought, "What shall I do now? Brahmaa must have created everything, I will therefore destroy, cutting off my own seed." As he had said this, a flame came out of his mouth and it burned everything.

When Brahmaa saw this, that everything was on fire, he bowed to him and praised him. Shankar got pleased by the praise and told him, "I am Shankar, I will always accomplish everything that is to be done for anyone who seeks refuge with me. Now tell me what should I do with that excess energy which I gathered to destroy you creation. Tell me your desire." Hearing this Brahmaa Jee thought for a while carefully for the welfare of the world, and said - "O Lord. If you are pleased with me, let your energy enter the Sun, since you are the Lord over the Sun, for you are the creator, protector and destroyer. Let us live together with all the immortals in the energy of the Sun, and we will receive the sacred image of the three times (past, present and future) that was given by mankind. Then, at the end of the eon, you take the form of the Sun and burn this Universe at that time."

Shankar agreed to this and laughed, for he was secretly amused, and he said to Brahmaa, "There is no good use for this Ling except for the creation of progeny." And as he said this, he broke it off and threw it upon the surface of the Earth. The Ling broke through the Earth and went to the very sky. Vishnu sought the end of it below, and Brahmaa flew upwards, but both could not find the end of it for all their vital effort. Then a voice arose out of the sky as the two of them sat, "If the Ling of the god with braided hair is worshipped, it will certainly grant all desires that are longed for in the heart." When Brahmaa and Vishnu heard this, they and all the Divinities worshipped the Ling with their heart set on Rudra.
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Hindu Religious Literature - Ved
(p 129-131) Ved are the earliest literature. In the beginning there was only one Ved, but considering it difficult to grasp, Maharshi Ved Vyaas Jee divided it into four parts - Rig Ved, Yajur Ved, Atharv Ved and Saam Ved.

Rig Ved consists of religious hymns, which probably did not reach its final form until about the 6th century BC; but the earliest parts of which may go back as far as 1300 BC - approximately the fall of Myeenean Greece in Europe. It is collection of 1,028 hymns, not all directly religious. Its main function was to provide orders of worship for priests responsible for sacrifices which were very common to the religion of Indo-Aryan.

Two further texts also began to be created towards the end of the period in which Rig Ved was being written down - the Yajur Ved and the Saam Ved. They also served the same purpose as Rig Ved. The Atharv Ved is largely a collection of magic spells.

Braahman 
Braahman is a collection of some books. Central to the Vaidik literature was a belief in the importance of sacrifice (Yagya). After some time, after 1000 BC, a second type of literature began to take shape - that was story telling as a means to interpret the significance of sacrifice. The most famous and most important of these were the Upanishad - probably written at some time between 7th and 8th centuries BC. The composition and writing of these classics was thus taking place approximately at the same time as the epics of Homer was taking shape being recited and ultimately written on the west coast of what is now Turkey.

Mahaabhaarat and Raamaayan
Braahman gave their name, Braahmanism, to the religion emerging between the 8th and 6th centuries. Two texts from about the same period remain the best known and most widely revered epic compositions - Mahaabhaarat and Raamaayan. The details of the great battle recounted in the Mahaabhaarat are unclear, but tradition puts its date at precisely 3102 BC, the start of the present era (Kali Yug); and also suggests that the author of the epic was a sage named Ved Vyaas. The evidence suggests, however, that the battle was fought around 800 BC at Kuru Kshetra. It was another 400 years before priests began to write the stories down. Although it could not be completed until 400 AD. The Mahaabhaarat was probably an attempt by the warrior class (Kshatriya) to merge their ideas with the popular Braahman religion. It was an uneasy process which took hundreds of years to complete.

The original version of Mahaabhaarat was probably about 3,000 stanzas long, but now it contains over 100,000 - eight times as long as Homer's Iliad and the Odyssey put together. The arguments about the battle between Paandav and Kaurav, were elaborated and expanded until about the 4th century AD, by which time, as Shackle says, Braahmanism had absorbed and set its own mark on the religious ideas of the epic; and Hinduism had come into being. Geetaa is comparatively a later addition.

Vaalmeeki is thought to be the author of the second epic Raamaayan, though no more is known of his identity than is known of Homer's. Like the Mahaabhaarat, it also underwent through several stages of development before it reached its final version of 48,000 lines (24,000 Shlok).

Others
Paanini's grammar of Sanskrit language helped to establish grammar as one of the six disciplines essential to pronouncing and understanding the texts of the Ved properly and to conduct Vaidik rituals. The other five were Phonetics, Etymology, Meter (Chhand), Ritual practice, and Astronomy (Jyotish).