As far as I know, Hinduism is the oldest and the most ancient religion among the five and in fact they don't call it religion but as a way of life coz every person born in India are automatically called indian or Hindu! The bible of the jews and christians were not yet written during that time. The sacred scripture there was
THE BHAGAVAD GITA AND
THE VEDAS which includes THE UPANISHADS!
Hinduism: Since Sanskrit is the oldest written language, as far as religion being written down, and as far as organized religion is concerned, it would be Hinduism. It is said that when Rama appeared, according to our calendar, was a million or so years ago (not sure of the exact date, but it's a long time!) And Krishna, God himself according to the Vedic scriptures, appeared here 5,000 years ago. Buddha, about 500 B.C., Jesus, about 2,000 years ago. If you go through the different religious book and study this question deeply, you will find out that Hinduism is the oldest religion of the world. There are no dates and facts, but its history is about more than 50000 thousands years ago.