How do iPhones acquire date and time? Do iPhones and iPads with cellular network support NITZ or do they only rely on NTP?
From the Carrier.plist file - iOS does support NITZ. Here' the refference on theiphonewiki.com.

Network time sync
&lt;key&gt;SupportsNITZ&lt;/key&gt;
&lt;true/&gt;

Enables time updates through the NITZ protocol.