Hi Manju,
__time when stored in Druid does not contain timezone information ... I believe the actual value will be stored as a LONG.
In general we think of the __time values ingested as being in UTC by default, but there are timezone parameters in various functions and granularity specs that allow interpretation of the data to be in a timezone other than UTC.
I believe segmentGranularity and queryGranularity do support timezone parameters at ingestion time ... however I have not used it myself directly so unfortunately I cannot provide any detail on the behavior here.