Best way to deal with summer time ?

Best way to deal with summer time ?

Hello,
This weekend we had to change hour in a lot of countrys, this impact my indicators because the office opening time is an important information.
I found a formula to take this in account but wontering if there is a better way to do it.

I am in France and my original data is a GMT Unix Timestamp

if((month(from_unixtime("calls.started_at"))>3 and month(from_unixtime("calls.started_at"))<10) or (month(from_unixtime("calls.started_at"))=3 and day(from_unixtime("calls.started_at"))>26) or ((month(from_unixtime("calls.started_at"))=10 and day(from_unixtime("calls.started_at"))<30)), convert_tz(from_unixtime("calls.started_at"),'+00:00','+02:00'),convert_tz(from_unixtime("calls.started_at"),'+00:00','+01:00'))

It's fine for now, but I'm not happy with hard coded parameters.

Regards,
Franck