ChatGPT tries but fails here. The answer is 100 microseconds, a micro-day is 86.4 ms, a nano-year is ~31.6 ms, either are widely used for anything. 0.001 s and 1e6 ns is 1 ms, Score 1/3 so far BTW Excel stores date/time as 64-bit floating point days, tme is fractions of a day