Thank God, the time sensor requires values compliant with ISO standards, which include time offset information.
It opens possibilities to automatic conversion from source to target offset/zone chosen by a user, including DST transitions. Unfortunately, it seems HA doesn’t make use of that. At least not in UI.
Regardless time sensor contains valid values, native Lovelace cards don’t translate those values into local time. I found no option for that. If sensor gets data in GMT, the only option is to display them in GMT. IMO such a value should be converted at least to local time determined from underlaying OS. The best option would be if the cards themselves can optionally convert to the timezone chosen by UI creator.
Another issue I found in Entities card is using ‘yesterday’ for the event which is a few minutes old.
For example If sensor state points to 23:55 but at the same time current time is 00:05, then the entity card shows “yesterday”. I believe it’s obvious to everyone that such a representation is completely useless. I understand the attempt of humanizing the GUI but this time it misses the mark. BTW similar behavior can be observed for “last changed” values. How one can even think of it as a useful feature?
Both those issues escalate when comped together. Having a sensor with data stored in GMT, while leaving in Central Europe with +2h offset during Summer, if the sensor gets the current time value at 0:30 of my local time, GUI immediately shows yesterday… Because in GMT (0-hour time zone), there is still a previous day (compared to my local date). Really? So the GUI just ignores that timezone piece of information. This time it’s not a matter of representation. it’s providing false information!