I have a number of Tasmota devices and over the years have not been able to figure out how to have Tasmota account for Daylight Savings Time. To manage this I created a Publication List with each of my Tasmota devices using a replacement variable. The replacement variable contains the timezone offset.
Another technique to change a common setting in a number of Tasmota devices is to use the Group topic setup in Tasmota. This approach would use a single MQTT message to the group topic and all Tasmota devices on this group topic would receive the message. The Tasmota Group topic is defined using the command "GroupTopicx topic" where x is group in range 1 to 4 and topic is the group topic name. The default is for a single group topic. For more recent Tasmota releases it is "tasmotas". For earlier it is only "sonoffs" and no x suffix is used. So in this example the publlist would be a single line "tasmotas/cmnd/timezone=-7". For this second technique to work one needs to use a different group topic when devices span multiple timezones.
Another technique to change a common setting in a number of Tasmota devices is to use the Group topic setup in Tasmota. This approach would use a single MQTT message to the group topic and all Tasmota devices on this group topic would receive the message. The Tasmota Group topic is defined using the command "GroupTopicx topic" where x is group in range 1 to 4 and topic is the group topic name. The default is for a single group topic. For more recent Tasmota releases it is "tasmotas". For earlier it is only "sonoffs" and no x suffix is used. So in this example the publlist would be a single line "tasmotas/cmnd/timezone=-7". For this second technique to work one needs to use a different group topic when devices span multiple timezones.