Ah nice, I tried that some time ago (with only AT+CCLK?) but that only replied an offset (since the modem was powered on) of the preset time.
I’ll try that some time with the +CTZU command 
.
By the way, is there a simple way to determine the next change of a daylightsaving? Even the google-api just tells the current state not the change-dates … I don’t want to lookup the time that often and maybe just store the dates and determine it locally.
Edit: I tried it and it sadly looks like my carrier (Vodafone in Germany) doesn’t support that feature 
. It responds with success but the offset is always 0.