Sure, it would be nice if the radio clock had the accuracy of a Stratum-1 time source, but that would make it prohibitively expensive for the display-only duty it serves.

Crystal oscillators drift depending on environmental conditions, so equipment that requires stable clocking usually employ temperature controlled oscillators (crystal ovens). This is commonly seen with telecommunications and test equipment that I work with every day. Mechanical shock can also affect oscillator operation... so in a vehicle you have both wild temperature swings - both extreme cold and extreme heat in the vehicle interior, as well as mechanical shock. Every time you start the vehicle you cause a voltage drop that may have the potential to affect the clock's accuracy. In light of all that, I accept the fact that the radio clock may drift and therefore take the opportunity to reset it when I am waiting for something else while sitting in the truck.

Now for GPS equipped vehicles, it would certainly be nice for it to synchronize to GPS satellite UTC since GPS requires extremely accurate timing to work at all... but hey, I've worked on multi-million dollar telephone switches which are hooked up to some of the most accurate time standards out there for time division multiplex clocking... yet the time-of-day in the system still drifts because no one felt the need to tie both components together in the system.

 

same issue here. i was going to start a thread about this to see if it was a common issue, but someone beat me too it and confirmed the fact that its not just my truck! and a minute a month pretty much sums it up!