If you still have a “dumb” pump like me (OmniPod Dash, no DIY looping), then remember to change back to standard time if that applies to you where you live. 
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Actually, in my Loop version, you have to change the time zone manually too.
Not sure if this applies to other Loop versions, but on mine, I have to do that.
Not sure why they did it that way. I think the idea is so it does not do it by itself, in case you travel or whatever.
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Last Tuesday I flew from Texas to Connecticut to be with my in-laws. We attended a Mass for my wife and then had lunch. Here’s the clan:
About pump and time change, after I landed I was notified and did the change, later today a12:30 PM to 11:30🤪got notified again because I set the pump to 11:30PM.
Maybe I’ll do it right Tuesday in Texas. Hope the Air Traffic Controllers are working.
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With AndroidAPS there’s a warning to “set a profile” but that doesn’t work, at least not with Omnipod Dash, and the closed loop gets suspended for 3 hours (I think, I was asleep). There is, however a button “set time” which appears magically on the Omnipod page and that is all that is required.
I find it incredibly dumb. I don’t have any settings that vary by time-of-day at but even if I did the pump and/or AIDS can see an extra hour has to be inserted (in this case) and can work out a safe way to do this, much safer than most people can manage at 1AM in the morning.
That’s certainly a bug. These days times are (and should be) kept in UTC with an offset; the bad of DOS days of using “local” time are long gone. Both the pump and the controller should do this and, I argue, should also know how to do timezone adjustments safely; summer time is just a different time zone, same as flying from the west coast to the rockies.
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How would the pump know a time zone was crossed? It doesn’t have WiFi or gps with no connection to anything but a CGM unless cabled to a computer.
I suppose that it could sync to the phone time that it’s paired too.
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I didn’t do it on Liam’s and it’s still working, so I guess it was addressed in later versions.
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At present primarily because the associated ‘phone based controller knows (not always correctly). Anything with cellular connectivity knows because the cellular networks expose the time zone (sometimes incorrectly), lots of things have cellular connectivity. For example my wife’s “free” BG meter (paid for by her insurance) has cellular connectivity. It rarely works where we live but it certainly has it.
The Omnipod has it’s own internal clock, which drifts a mile a minute, and, apparently, a 24 hour offset. I don’t think it knows calendric time and I can’t think of why it would; it’s useful to allow basal rates etc to vary by workday/restday but it doesn’t support that.
I don’t think WiFi helps. I am not aware of a way to discover the local time zone from a WiFi network, there may be proprietary extensions; I looked at DHCP. It’s certainly a bug-by-omission and it’s not WiFi specific.
GPS doesn’t help either; it’s not enough to know where you are, you also have to be fully up-to-date with the local law. The way this is done on ‘phones and computers in general is to have a truly massive local database of time zones for everywhere on this planet which is assiduously updated for free by volunteers.
There’s more information about how it is done on the internet 
A lot more
If you read the whole thread and skip the dipshits you will not learn how time zones work but you will, curiously, lean why the internet works.
[quote=“jbowler, post:7, topic:15519”]
GPS doesn’t help either; it’s not enough to know where you are,
[/quote
Telecommunications switching including cell phones use the clock fro GPS satellites to sync everything together. This is not just a timing pulse but gives ultra precise time. None of this equipment gives a toss about location because they are stationary. We had backup clocks that were not as precise in the event of a loss of GPS signal.
@CarlosLuis I think it may be due to some folks having their phones set to automatically detect local time and then the apps notice a clock variance between what “it”, the app, has set and what time the phone reports being set. I might have the terms a bit off, but I believe that is how Loop and Trio work. On Trio, I get a warning banner across the top of the screen when the phone updates from EDT to EST or vice versa; when clicked the app asks if I’m sure I want to update the app to phone’s time. Save goes when I change timezones when traveling.
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@TomH in open loop the pod is 100% controlled by the phone app iirc So when the pod and phone clock disagree the app changes the time in the pod both time zone or standard/daylight saving.
The Tandem T slim app only shows history and current IOB and BG. The latest version allows to bolus with the app, but not extended.
Tandem Mobi is 100% controlled by the phone app. I assume it will automatically keep the time date to the phone. I have a T slim.
Who knows about Medtronic pumps not me
That is correct. On Android the setting is, currently, (Android 15, but it hasn’t changed recently IRC), Settings/System & Update/Date & Time/”Set time zone automatically”. There’s a similar setting somewhere in iOS though no doubt in a confusingly different place.
In principle the ‘phones could use the GPS and zoneinfo but I don’t believe that they do; that’s not what I see. Rather I see the timezone update when the ‘phone connects to a cellular network. It does not have to be able to use the network; it seems to be sufficient to connect to check if it can use it. I may be wrong; this is certainly not FOSS, it is most likely highly secret and completely undocumented.
It may be that the GPS and zoneinfo are being used (GPS update takes a while, just like connecting to a cellular network). I just don’t know; my conclusions are based on seeing it go wrong, something I have not experienced with zoneinfo.
I have a Mobi. It does not automatically update time, but if the time on the phone changes and does not match the pump, the app will alert with a message asking if you want to set the time to match the phone.
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Now that is a misdesign if I ever saw one.
I use standard Loop DIY software with a MM 722 pump and Dexcom G6 CGM. When I awoke last Sunday morning, The Loop dashboard showed a small clock icon that alerted me to the time change. I have gone through this many times in my 9 years with DIY Loop.
The key thing for me to remember is to change the time on the pump using the Loop software and not directly using the pump buttons. Each successive iteration of the Loop software has made this change easier to execute. All I had to do was click on the clock icon alert. Easy.
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I see that my knowledge of open loop needs some remedial education. Until now I thought that open loop was only for OmniPod Dash pumps. Thanks for reducing my ignorance.
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A limited number of older MM pumps were used in DIY Loop around 2016. Loop software expansion in 2019 made it possible for some Omnipods to utilize Loop. But the quantity of Omnipod Loop users was huge compare to the more limited older MM model users. When Loop opened the door to Omnipod users, the MM DIY users became an instant minority.
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Thanks @Terry
But it leaves the user in control, which I (using a Mobi) appreciate!
Its helpful when we travel across the country to visit family every year … my body does NOT accept a 4hr time change overnight and I pretty much keep my pump on whatever timezone best matches my breakfast ratios to when I eat breakfast. I have a higher I:C ratio for breakfast vs other times even if that means I am not getting up until noon local time.
And then a very small use case, but this past summer I drove from central/interior Alaska to the panhandle/southeast Alaska which requires crossing the Canadian border into the Yukon and then dropping into BC for a bit before crossing back into AK. As best I could tell, I went through 3 time changes to end up back in the time zone I started in, and while it wouldn’t have made a clinical difference to keep hopping forwards and backwards by hour here and there, I appreciated that I got to decide if I needed to adjust my pump timing to this new zone or was I just driving through.
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