Exact age in whole years, months and days plus days/weeks/hours lived, the weekday of birth, the next birthday and its countdown. Dates are calendar dates in UTC (no time zones or times); 29 February birthdays fall on 28 February in common years; leave the reference date empty to use today. Impossible dates (2023-02-30) and birth dates after the reference are reported per line. Everything runs locally.
Age is measured up to this date.