ref: e8f5e0909f4a7c7ae2c4e85f563e6b4da88aa98f dir: /sys/src/ape/lib/ap/gen/difftime.c/
#include <time.h> /* Difference in seconds between two calendar times */ double difftime(time_t t1, time_t t0) { return (double)t1-(double)t0; }