RTC hardware accuracy

Has anyone got any data on what RTC accuracy I can expect ?

This is a hardware question, not a software or operational question. By which I mean how much can I expect the RTC hardware to drift assuming it is not periodically synchronised to anything ?

I’ve been doing some experiments using R4 pips (old-fashioned analogue radio) and accuracy appears very good so far, with no discernable drift (less than one second) over a number of days. But that’s just one module, some data would be nice. Can’t find anything specific in the data sheets.

I have no idea whether ot not RTC is being synchronised from an external source (eg network) but I think its safe to assume not. Certainly I haven’t set anything up (and wouldn’t know how, my Q2686 is more or less ‘as new’) and judging from other forum posts this is unlikely to work anyway, and certainly not something I can rely on, since few network providers seem to support it.