extern int taia_now(struct taia* t);
taia_now puts the current time into t. More precisely: tai_now puts into t its best guess as to the TAI64NA label for the 1-attosecond interval that contains the current time.
This implementation of taia_now assumes that the time_t returned from the time function represents the number of TAI seconds since 1970-01-01 00:00:10 TAI. This matches the convention used by the Olson tz library in “right” mode.
Beware that many clocks are not set accurately, and even the best scientific clocks are nowhere near 1-attosecond accuracy; however, an inaccurate clock may still produce reasonably accurate time differences.