ref: 1a5dafcc3d8c455b0e7b36dd9bd45c13dd4d91eb 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; }