'In my experience generating accurate time bases with electronic circuits based on resistors and capacitors is very hard to do -"
Perhaps not that hard if temperature is held constant. One could probably design a clock that is very accurate if the temperature is held at some constant, like for example 25C, standard room temperature, however if the temperature is allowed to vary then it might run faster at higher temperature and slower at lower temperature. As a test, you could take a digital watch and keep it in a refrigerator(in a sealed plastic bag to protect it) for a few days and see if it ran slow. I guess even a mechanical watch might run slower at a colder temperature.
