1. 01Choose the birth date.
2. 02Confirm or change the reference date; the birth date cannot be later than it.
3. 03Read the four cards for exact age, nominal age, zodiac animal and star sign.
4. 04Read the cumulative months, weeks, days and hours, and the date, weekday and remaining days of the next birthday.

• The birth date must not be later than the reference date, otherwise no result is shown.
• The zodiac animal, star sign and the lunar-year nominal age depend on the on-demand lunar-javascript module; if it fails to load, or the date falls outside the calendar range, the zodiac and star sign may be empty and the nominal age falls back to exact age + 1.
• Total weeks are the integer part of total days divided by 7; total hours are total days × 24 and do not include a time of birth.
• The next birthday is derived from the date; the tool accepts only year, month and day, with no birth time or time zone.
• What it does not do: it does not store several birthdays, does not replace a countdown manager and does not analyse the full interval between two arbitrary dates.

The birth date and reference date are computed in the browser only; the lunar-calendar capability comes from a dependency bundled with the app and does not call an external calendar API.