Flexpoch: Feature-rich 64-bit DateTime Encoding

The 32-bit Unix time, which is commonly used in computer systems, will overflow on 2038-01-19. Extending the format to 64 bit would allow to count seconds for 584 billion years but misses the opportunity to add features, such as sub-second precision or relative time encoding, which are useful for a universal datetime encoding.We propose and implement Flexpoch, a versatile 64-bit time encoding that is compatible with Unix time, has a high range of 21 thousand years, supports leap seconds and timezone offsets, and offers multiple precisions from 119 ns to millennia while being highly resource-efficient.