The time on digital camera clocks can run fast or slow, depending on different factors.
It is called "clock drift".
BBM
"Consumer-grade digital cameras have become ubiquitous accessories of science.
However, such devices were never intended for precise timekeeping, and their use as such needs to be accompanied by appropriate management of systematic, rounding and random errors in reported image times.
Camera clocks drift and the drift can be substantial: daily subsecond to second drift can accumulate to multi-minute offsets within a few months."
Cameras as clocks | Journal of Glaciology | Cambridge Core