ref: 267e3cc41aa9aed63f2b9f7e9b69ef0b49f3c7c7 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; }