"According to ISO/IEC-14496-5-2001, the difference between Unix time and Mac OS time is 2082758400. However this is wrong and 2082844800 is correct."
MP4 stores timestamps by Mac epochs. The wrong value of the difference between Unix and Mac
epochs is wrong exactly by 24 hours and is hardcoded in the MPEG-4 reference software, from which it made its way into a number of libraries.
(I work for Google and have contacted the right people in the attempt to address this bug soon).
To finish the puzzle, consider the following comment in one open-source mp4 library: https://github.com/l-smash/l-smash/blob/master/core/box.h
"According to ISO/IEC-14496-5-2001, the difference between Unix time and Mac OS time is 2082758400. However this is wrong and 2082844800 is correct."
MP4 stores timestamps by Mac epochs. The wrong value of the difference between Unix and Mac epochs is wrong exactly by 24 hours and is hardcoded in the MPEG-4 reference software, from which it made its way into a number of libraries.
(I work for Google and have contacted the right people in the attempt to address this bug soon).