I could be mistaken about the following since I haven't run this by anybody else, but I was under the impression that most Indian visas issued are only valid for staying in India up to the date of visa expiry stated on the visa; and that for those who will be in India visiting beyond the printed visa expiry date a renewal/extension is required, but that ordinarily on a tourist visa they don't like granting more than half a month or so as an extension unless there are some kind of special circumstances. [Another visa -- at least in prior decades -- good for extending the stay -- worked out easier than trying to get an extension on an existing visa.]

Some countries and/or visa types have date of entry as the driving factor while others have it as the date of issuance, and it can be such a mix that it confuses even those in the consular sections. I operate on the risk-averse presumption that Indian visas aren't good for use to stay in India on or after the expiration date entered on the visa itself at time of visa issuance.