ref: 2c1dc1aa4f374f5c8d6a13e7e82a26c4e27e6775 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; }