Most Pii seem to consistently run about half a second fast per hour, or 12 seconds per day. It's a pretty simple matter to measure a particular Pi's rate of offset over whatever the maximum service interval is estimated to be (how long between opportunities to check for and correct problems), and use a script that applies that offset periodically in the opposite direction. Even the atomic clocks used by GPS, Network Time Protocol (NTP), and the standards bureaus have to institute a "leap second" periodically to account for an offset that accumulates from miniscule errors over a period of years. The number of atomic oscillations being counted doesn't precisely align with the number that's actually needed to maintain a 100% accurate rate, plus the rotation of the Earth about its axis and its orbit around the Sun are slowing down almost imperceptibly over time.
The best things in life aren't things ... but, a Pi comes pretty darned close!
"Education is not the filling of a pail, but the lighting of a fire." -- W.B. Yeats
In theory, theory & practice are the same - in practice, they aren't!!!