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So it looks to me like the above service is a read only service.
There's another service called the Reference Time Update Servce (RTUS) that has a write-enabled component.
Say you have a phone & a trusty Broadcom 737 TAG board, you're developing a device that has a RTC feature & want to be able to set the time on the device from the phone.
It looks like the (RTUS) would be the service that the phone would initially engage to set the time on the device. However it looks from the characteristics of the RTUS that all you do is issue a start-type command that initiates getting the time from some other source (like an NTP).
There doesn't appear to be provision in the RTUS to pass it a time & set the time directly through it. The Current TIme Service (CTS) is all read only so there's definitely no way to pass it a time to set.
So, am I missing something? If you wanted to set the time on a device using a phone would you have to implement you're own service?