It should not be Analytics bug. Usually bounce visits get market with 0:00 time, if people come to your website and leave it instantly Google gets it as bounce

Shailender,

To elaborate a little on what conqueror has said, Google can only calculate average time on the page by measuring the time between the first pageview and the next pageview generated during the session. When a visitor does not go to another page on your site, no second pageview is recorded. Therefore the TOS appears as 0.00 even if the visitor spent a lot of time on the one page.

Best,

Shawn

Thanks TheContentAuthority,

You really explained the answer easily and in short. Thanks again.