Tslim pump time incorrect

Has anyone noticed the time on the pump slows down over time? I remember syncing the time on my pump 2 weeks ago when I noticed it was a few minutes behind my phone. Today it’s again 2 minutes behind.

Yep, it’s a common problem. Supposedly all pumps lose time. I read a really good technical explanation of why the other day on Facebook, but now I can’t find it. So I’m just going to paraphrase the best I remember it…

There’s some sort of problem with their “brains” where they can’t keep track of the time and bolus at the same time. Maybe not enough RAM or processing power to do two functions simultaneously? Since the T:slim boluses slower, the loss of time is more evident than in some other pumps.

There’s also a problem with the quality of modern time processing computer chips (or whatever component is used for that). Since most modern devices update their time from the cell phone grid, quality of the time keeping hardware has diminished. Without paying a small fortune for fancy “chronometers”, there’s simply no good digital time keeping equipment anymore without a cell signal.


That’s interesting, I noticed the same thing. My pump is now 2 minutes behind, and I had them equal when adjusting for daylight savings time.

Wow in the age of modern technology and we still can’t manage to get the time right without spending a fortune to sync it! :flushed:. It’s probably the least complicated functionality on the pump. Kind of mind blowing really

Ahem… just checked my t.slimx2 and it is exactly the same time as my computer which is automatically sinc’d to grid. And I am in a place that is covered with dead spots for cell phones. I hand set my pump time to the computer 12 days ago when daylight savings time went out.


@Robyn_H‘s explanation is very good. Our phones, laptops, and tablets are not accurate because of some magical precision, but because they “check in” with international time standards multiple times per day for a correction. As a result, they always appear to be perfect … although, in reality, even they are fractions of a second off at time until their next correction.

Stand alone electronics … a thing with a computer in it … has a master “oscillator” in it that becomes the main clock signal that drives the computer or, in this case, insulin pump. You might have a computer that has a 5 GHz clock speed … which means that it likely has an oscillator in it that runs at a frequency of 5 GHz.

Of course, our pumps have a computer that serves as it’s brains … but it is not nearly as fast as you laptop, particularly since it needs to run for several days on a battery charge.

I have no idea what speed the processor in our pump runs at, but is is probably much slower than 5 GHz. Let me pretend that it is 100 MHz (that is, 100 million cycles per second. So, if you have a circuit that does nothing but count clock cycles, and then resets to zero, every time it reaches 100,000,000, then you have a nice, accurate one second interval. Problem solved! Perfect time keeping!

Except, due to manufacturing tolerances, the oscillator in your pump probably doesn’t run at PRECISELY 100.00 MHz. Suppose it runs at 99.99 MHz, then it takes a very small fraction of a second LONGER than one second for that circuit to count to 100,000,000. So what it thinks is a second is actually about 1/10,000 longer than a second. Since there are 86,400 seconds in a day, a clock frequency that is only 0.01% slow will actually lose 8.6 seconds per day. If your computer clock is slightly faster than my mythical 100 MHz, then it will actually gain time.

Computer lesson over … you all get A grades in my class.

Stay safe!



I seriously love how much information this community has to share!


Since this was raised, could this have anything to do with a new problem that started today?

My T:Connect App has been auto-updating fine, until yesterday. It would not update every 5 minutes, but if I exited app and went back in, it was correct.

So after this discussion, I updated pump to have time identical to phone, and T:Connect now refreshes as expected.

I don’t think so, this time issue I’ve noticed for a while now.

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Couldn’t agree more :grin:

Of course keeping PRECISE time isn’t really important on a pump, is it? I don’t think that it affects dose accuracy.

Speaking as a retired technologist … I was a first-year grad student working on microelectronics (AKA chip technology) back in 1972 … I continue to be amazed by the things that we have access to today. Just think about a smart phone: a combination of a sophisticated computer, high resolution graphics, HUGE amounts of memory, cell phone technology, WiFi, BLE, GPS, fingerprint or facial recognition, speech synthesis and recognition … it is all mind bogglingly complex. Yet, we all seemingly can’t function without one … Turn by turn directions to anywhere? Really? I hope I never lose sight of how amazing this stuff is. None of the above things that I have listed was remotely possible at any cost in any form factor when I started grad school in 1972.

But, so that this is remotely relevant to diabetes … 1972 was also the year that I developed T1D. And I’m not troubled that my pump doesn’t keep perfect time … my phone does that.


It doesn’t but is annoying when my CGM dot reading should appear on the 2nd and 7th minute and it suddenly doesn’t. And then I look on my Dexcom app on my phone and that also is out of wack. While 2 mins is nothing, if left uncorrected for months turns into many mins … enough to make a difference when analysing data on your reports. Also enough to meet up with daylight saving eventually :joy:. Then again could end up 2 hours behind eventually too depending whether daylight saving is backwards or forwards :thinking:.

Yes apparently we have more processing power on our smart phones today than on a state of the art super computer 20 years ago. We have come a long way… and the time on my pump is still off :joy:. Ironic don’t you think?

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My pump is exactly the same as my phone.
I adjusted it when the time changed.
I can’t remember if it was off at that time.
Why can’t the pump ping the time when it sends data to the phone.
This seems like a silly and easily remedied issue.
I don’t wear a watch because I just look at my pump for time usually.
If I’m late for work now I have a good excuse.


Never thought of that but it makes sense. In-built time keeping as a vestigial function falling into atrophy as other “organs” take over. Evolution baby—sometimes it hurts.


Yes, I think that this is the obvious solution. However, if I look at the way that the Tandem t:connect phone app behaves, I can’t acknowledge an alarm on my phone and have it “clear” it on the pump. This leads me to believe that the BLE communication is currently only broadcasting from pump to phone but not listening to responses from the phone.

I’m hopeful, however, that an updated version of both the pump software and the t:connect phone app WOULD allow two way communications because it would be really nice to clear pump alarms from your phone. At that point. it should be easy for the pump to ask: “ Mr. Phone, what time is it?”

Of course, since I have no inside knowledge of the exact communications between phone and pump, I may be completely wrong about one way vs two way communications between pump and phone.

Stay safe!


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Bonus question: why is your cheapo electric bedside clock so accurate?


I hope you have the answer :sweat_smile: because :woman_shrugging:t2:


Because it’s connected to the electric grid, which runs at a reliable 60 Hz (asssuming you meant a clock plugged into the wall).