[PWG5100.14] Issue #117: Add requirement for Clients to include the "Date" HTTP header in all IPP requests

[Issue Unconfirmed]

Some Printers lack a battery-backed clock, support for the Network Time
Protocol, or NTP is blocked by their network. In these cases, it is useful
to set the printer's clock via some fallback method other than human
interaction. If all Clients provided the "Date" header with the current
date and time, that would let a recently powered on Printer to set its
clock using the value received.

Link: http://www.pwg.org/issues/117