There is issue in grafana where it checks time as UTC time but when in interval comparison or group by it checks time as local and only converting interval time to UNIX .
Solution - You should add one more column to table which should contains UNIX equivalent time of your timestamp and pass that in time column and everything will work.
Eg.
Local Browser Time - 2020-05-31 17:21:05 (It is UTC + 5:30)
UNIX_TIMESTAMP - 1590945665