ref: ca2fa9596b5d0d893be28c6e8fd8a52a89a0c3c6 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; }