ref: 2db3642b8d3b871c6f9d1f4e3204b2f44fc4b79f 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; }