A while back I built a project that has a DS3231 RTC generate interrupts to a Pro Mini from time to time. Two months ago, I synced the DS3231 time to the website time.gov , and today I checked it against that same site. After two months, it was 4 seconds fast, which annualized is 24 seconds. I had…

Good post. Can you explain more about the aging register? I have messed with a ds3231 module a little, but no long term projects.

Thanks for sharing! Posting some simple code showing how you adjust it and how you determined how much to adjust it would be great. I use the same part and I have found it very close. My system checks it every 8 hours and it may find a second now and then but there is no provision for network lat…

[image] scottcalv: Can you explain more about the aging register? The Aging register is register 0x10. It contains a signed byte (int8_t), which means its value ranges from +127 to -128. The default value on power up is zero. A higher value makes the oscillator run slower. This register i…

[image] gilshultz: Posting some simple code showing how you adjust it I don't use a library for the DS3231, so my code is pretty simple: Aging = readReg(0x10); writeReg(0x10, Aging); byte readReg(byte regAddr) { // read RTC register Wire.beginTransmission(RTCaddr); …

[image] ShermanP: My setup promotes good timekeeping...in a project box inside my house will check again in a month or two :rofl: Dump the ProMini/RTC and replace it with a XIAO ESP32-C3. The ESP can get time off the internet. Accurate within 1 second, forever. Including daylightsavings if…

[quote="ShermanP, post:5, topic:1442298"] Aging = readReg(0x10); writeReg(0x10, Aging); Thanks, many will appreciate the code and explanation. I appreciate the lack of a library, I use as few as possible.

Following up on this 30 days later, as compared to time.gov , the DS3231 is now two seconds fast, down from four seconds fast. So changing the aging setting by one slowed it down by two seconds in a month. So to recap, with aging set to -5, it gained 4 seconds over two months. With aging set to -4…

[image] ShermanP: changing the aging setting Have a look at this: DS3231 Service Tool

Yes, it looks very helpful, but I had already included its functions in my project code. I forgot to report that I adjusted the aging setting on July 1st. It again was almost two seconds fast, but I just changed aging by one to -2. I probably need to be making larger changes, but this illustrates…

[image] ShermanP: As for how much to adjust it, I used to remember how much a change of +/- 1 would produce, but I've long since forgotten that. So you just need to experiment. From the datasheet at https://www.analog.com/media/en/technical-documentation/data-sheets/DS3231.pdf The change in…

Report on DS3231SN timekeeping performance

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InquisitiveMind July 17, 2026, 10:41am 9

Have a look at this: DS3231 Service Tool

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Report on DS3231SN timekeeping performance

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