Does Vedic astrologers of the old days really have means to measure time accurately?

I often wondered, if Vedic astrology is so dependent on the accuracy of the birth time, right down to the minutes, how do the ancient astrologers measure time? If there is no effective way of tracking time to such precision, will that imply astrology is simply hogwash, despite its antiquity? Well, in Jaipur, North India, there is an astronomical observation site called the Jantar Mantar, which was built in the early 18th century (1739 to be exact). It includes a set of some twenty main fixed instruments which were blown up to astronomical (pun) size. One of the most important instruments is known as the Vrihat Samrat Yantra (great king of instruments), which is the world’s largest stone sundial. How accurate it is? It can predict the time with accuracy up to within two seconds! Therefore, we know that more than 2 hundred years ago, the ancient Indians really do have already an effective way to measure time with such amazing accuracy. The following video will show you a close look of these instruments:

Ancient Indian Astronomy