Hello,
I am not familiar with specific requirements for time zones for m2m SIM cards, and would advise to consult your provider.
My assumption is that the time zone must match the network's it is connecting to.
I would like you to check, if you you are able to automate time zone setting and if the device is able to connect. First, login to router's WebUI, navigate to Services -> NTP -> NTP. Under Time Synchronization section enable Timezone synchronization option. Next, change device's time zone, and see, if it is able to recover correct information by itself as well as establish data connection.
Best regards,