Hi Brian, At some point I created a slidedeck explaining some of the things to consider when working with dateTime fields. Feel free to take a look at these slides. Be aware these examples are from Mx5.5 and DateTime has improved significantly for the better so some examples in this file might no longer apply to Mx6.
However the important aspects such as when to use localization and what to remember still applies in Mx6
Additionally to Japser's link to the slide deck see https://world.mendix.com/display/refguide5/DateTime+handling+FAQ in the documentation, it explains a lot.