From when will, any new taxes that may be announced in Indian Budget 2011, come into vogue?

Suppose that new taxes are proposed on a particular item (TV, for example) in Indian budget 2011. From when will these new taxes become applicable? Is it from the moment the budget is announced or is it from April 1st, 2011, as I have heard from somebody? With reference to our little example above, this information could be helpful for somebody who wants to buy a TV set before the new taxes become applicable.
Thanks in advance.