Last time I checked three years ago, the UEFI spec states that the hardware clock (rtc) is set to "current local time". UEFI runtime service's GetTime() include

Last time I checked three years ago, the UEFI spec states that the hardware clock (rtc) is set to "current local time". UEFI runtime service's GetTime() includes TimeZone value in minutes offset from UTC, and a Daylight bitmask. Windows, Linux, macOS, all set the timezone value to 0x07FF which is defined as EFI_UNSPECIFIED_TIMEZONE which is to be treated as local time (but without a timezone). In effect, it's the same mess as BIOS. It shows how specs can just be thwarted.