[AusNOG] Mobile network-provided time zone

[Paul Gear]

Hi all,

In the past 10 or so years, I've used every major mobile carrier's
network, through both the carrier directly and often through various
resellers, and one thing remains consistent.  Every year on this
weekend, when in Queensland, the network-provided time zone changes to
UTC +11 (Sydney/Melbourne).  This is very handy when roaming overseas,
but not so handy when it changes your time zone when it shouldn't.

What's causing this?  I know it's not NTP on the handset - I know a
little about that, and it doesn't include time zone in packets, nor does
it care about time zone when it adjusts the kernel.  I assumed that this
feature was implemented on the mobile network side, and the mobile base
station broadcasts its time zone along with the other information
handsets need to connect to it.  But I don't know enough about the
technical side of that to be sure.

The usual suggested remedy when I contact my carrier to complain that
they're sending my phone the wrong time zone is to ask for the handset
to rebooted.  Sometimes it works; sometimes it doesn't.  But why would
it make any difference?

Can anyone shed any light on this?

Thanks in advance,
Paul