Time Changes with Loop⌁
Loop is built to operate fully across time zone and daylight savings time changes as long as a few basic instructions are followed.
Always use RileyLink to change pump time instead of the Medtronic Pump's screen. If you fail to set the pump time by using the RileyLink, Loop will not function properly.
Loop will assume your iPhone's time (UTC, not timezone) is always correct. This theoretically may not be the case if a nearby cell tower is improperly configured (though there are likely resilience mechanisms in iOS to handle this). Automatic time setting can always be disabled in Settings.
Minimed Pump and CGM⌁
The Minimed pump doesn't expose a universal clock, instead it exposes the components of a date (YMDHIS). It has no concept of political time zones, and just continues to increment its components on schedule. Therefore, Loop assumes that the pump's date, until changed, remains at a fixed offset from UTC.
That offset is stored by Loop the first time the pump ID is changed, and every time the pump's time is changed from the RileyLink Settings screen.
No particular input is needed on your part for Loop to work with Dexcom CGM data. All times are UTC. However for Dexcom receiver users, at time changes you may want to manually change your receiver's time setting just so the time visually appears correct when you are viewing the screen.
Traveling across time zones and daylight savings⌁
When traveling, there is no urgency to update the pump's time to match the wall-clocks in your geography. Configuration schedules—basal rates, target ranges, carb ratios, and insulin sensitivities—will all remain in the pump's time zone. The app's graphs and status will always display in the time zone of the iPhone, and Loop will understand the difference in offset between the two, highlighting it when attempting to change configuration schedules.
When you're ready to update the pump's time, simply use the Loop's RileyLink "Change Time" command . This will also shift your configuration schedules to the current time zone.