I expect the local time zone can generally be assumed, but this would handle Daylight Savings Time for us. Right now, the data for 11/4/2018 01:00 does not distinguish EDT and EST. We get 2 measurements for some devices in that hour. For devices that have only 1 measurement, especially those that occur in the middle of the group for the hour, we can’t tell which hour the measurement is for.
It would be nice to have that tightened up.
AFAICT, Excel will not accept time zones as part of a date time format. If we wish to cater to Excel, 2 fields could be included one with and one without time zone.