ref: 65bd53b9b89b0a84d0f16db4adc3f53fa6ab3a3a 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; }