Why not just fix the time and date on the phone?
If only it were that simple!
What is the difficulty? If it is because you have users in different time zones, the user can set their tz under device management in UCP.
What @lgaetz said, and if the phones aren’t on the internet then just set the time on the FreePBX server and point the time server at the PBX.
Sorry, that was a bit tongue in cheek! There has been a problem for years with getting End Point Manager to set handsets (not just Sangoma ones) to set GMT+1 (for BST) on the correct date. So I always ended up putting in my own basefile edits to force the correct start/end date. These would mysteriously disappear during EMP updates. So twice a year I get loads of customers calling me saying that the time on their handset is wrong. So not having a date/time on the handsets would have remove a lot of hassle for me (don’t they have watches)!
Anyway, I think this is all behind us now and the BST does get set correctly with the latest EMP versions.