Why does email from an iPhone have the wrong time zone in the Date field?
The problem, I think, is with your mail client. The times in the headers are consistent, that is, the chronological sequence is correct. The issue is that your mail client is not translating the time given in the header into local time for display. This means that an email to you from, say, New Zealand would be shown in your mail client with a time that hasn't happened yet for you locally.

Verizon's cellphone equipment (e.g., ENodeB) is almost certainly set for UTC (alias GMT). That greatly simplifies their data aggregation issues.