My HP 5082-7300 clock uses a DS1302 RTC module to keep the current time. That kind of cheap module is known to drift, and mine obviously does.
After three months of operation my RTC is about 170 seconds late. With due approximation this means is looses 2 seconds every 24 hours.
The temperature inside my clock box is quite constant, on the high side, thanks to heat dissipation in 4x HP 5082-7300 early LED tech displays. Temperature is one of the two main causes for drift, the other being the 32768 Hz crystal not properly matched to the chip specs.
I am planning a firmware upgrade that adds two seconds every day, in the middle of the night. New version will be uploaded to my github.