ref: d5f2d2cc3fc7c2d3701e906df5d2d53781c4ee9c 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; }