I've used a RTC from Abracon, the AB-RTCMC-32.768kHz-EOZ9-S3. But it is a small SMT part 2.5mm x 3.7mm -
Wow! - regarding the specs and size. Seems to be what I was originally looking for. Only hustle looks to be the size. I've never soldered that package, but here is an opportunity to try something new
However, leaving an RTC running alone over that period, then the time is going to drift, probably a lot. Especially with temperature changes. Also, keeping it powered for long periods could also prove tricky. The RTC above has inbuilt backup supply charging for a small battery or super cap which at least allows you to ensure small periods of power loss.
Well it would run unattended for max of 2yrs (end case), and a day off is not a big deal, temperatures should be rather stable room temps (aircon allways).
I have no experience with Abracon, you're overall opinion is positive I guess in terms of reliability?
.. curious about the application
A friend and I are making like DIY playground for various laser heads he accumulated over the years, so there is a lot of stuff to monitor for "expiration date" - sensors, gases, coolants... As this is a side project for both of us, priority is low and everything is going slowly, and we're aware we'll forget to take care of something, so once we set something, setup the reminder. Usually the devices from which the laser heads originated had those monitoring systems in place, but we need an external one now.
Of course this could have been done with some cloud based calendar on a computer or a phone, but this is just us playing.
First idea was the most logical MCU+RTC+Relay+battery (CR1225 -small but just for prototype), but as a dare I started trying to make it as small as possible, so now it is DS1682(3)+power switch (AP22802) and the size od the PCB is determined by the holder for the CR2032.
Final idea is RTC+PWR switch + something like 1/2AA w/ axial leads, so the minimum size of the PCB would be determined by the size of the battery.
Not a big fan of a super cap for something that I don't know if I will power up tomorrow or next year.
Anyways, as I said it's a slow project and this is really just a small part of it, we've just finished the gas system (and this was expensive... e.g. 1m pipe for fluorine gas like 700eur, 2 stage fine reducers a lot more...) and the next priority is a modular optical bench.