ref: 1c30bd451e1813f1cf9f9db4d7c1a4f3f95d1e37 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; }