Binnacle Options - Clock vs Tachometer

So my clock keeps losing time - not sure how this is possible as it has a constant live Im led to believe?
Any pointers on this one? As its got me stumped? Cars got a new battery also.

But Im also thinking Id rather have a tachometer/rev counter instead of the clock - has anyone purchased one of the 52mm tachometers and swapped it for the clock? Amazon product

I understand on a 200/300 tdi it needs to be wired to the altenator?

I suspect most clocks lose time being analogue even digital non atomic suffers.

You need the special connection on your alternator for a rev counter, the letter of this connection escapes me now
Think it's 'W'...
Landrover clock has a resister or something that reduces the operating voltage I believe so it doesn't need a full 12v. As the rev counter connection, I'm unsure of that as well.