Isssue with date and timezone


I am facing problems about date and timezones. Suppose whatever post are displays in my screen that shows me 1days before dates. for eg. I have tweet on 30th April morning as per My IST (indian standard time), its shows me like “Randhir Mayatra ‏@RajMyt Apr 29”. Its for all tweets in my screen same kind of dates display. one day before date shows me.
I have set my Country as india so it should be detect my timezone. so its bug or I have make mistake in configuration…?