If your events have an incorrect time zone, then I suggest you set the correct zone at index time using TIME_FORMAT or TZ in props.conf.
If your events have the correct time zone and you want to display them in your local time zone, then change the time zone in the user settings. (Click on your username at the top and then click on "Preferences".)
If you want to shift the time of your events at search time (I believe this is want you want), then do this:
index=dcsdjc ... | eval _time=_time-7*60*60 | ...
This will substract 7 hours from _time. It works because _time is represented as Unix epoch time.
However, it will not update the date_wday and date_hour fields.