Return current TAI timestamp.

def tai_timestamp():
    """Return current TAI timestamp."""
    timestamp = time.time()
    date = datetime.utcfromtimestamp(timestamp)
    if date.year < 1972:
        return timestamp
    offset = 10 + timestamp
    leap_seconds = [
        (1972, 1, 1),
        (1972, 7, 1),
        (1973, 1, 1),
        (1974, 1, 1),
        (1975, 1, 1),
        (1976, 1, 1),
        (1977, 1, 1),
        (1978, 1, 1),
        (1979, 1, 1),
        (1980, 1, 1),
        (1981, 7, 1),
        (1982, 7, 1),
        (1983, 7, 1),
        (1985, 7, 1),
        (1988, 1, 1),
        (1990, 1, 1),
        (1991, 1, 1),
        (1992, 7, 1),
        (1993, 7, 1),
        (1994, 7, 1),
        (1996, 1, 1),
        (1997, 7, 1),
        (1999, 1, 1),
        (2006, 1, 1),
        (2009, 1, 1),
        (2012, 7, 1),
        (2015, 7, 1),
        (2017, 1, 1),
    ]
    for idx, leap_date in enumerate(leap_seconds):
        if leap_date >= (date.year, date.month, date.day):
            return idx - 1 + offset
    return len(leap_seconds) - 1 + offset