Putting two day counts side by side
Enter two dates of birth and the date you want to count up to, and both day counts come back together with the gap between them in whole days. The second field is optional, and leaving it empty simply reports that nothing was entered in the gap row. Add a target day count and the tool works backwards to the date each person reaches it, weekday included, so a round number such as 10,000 or 20,000 days can be marked on the calendar in advance.
A day count is the counting date minus the birth date, with the day of birth counted as zero. The date a target is reached comes from adding the target to the birth date, so leap days push it later by exactly that many days. Every date is assembled from UTC components, which keeps the answer from slipping by a day on a differently configured device. (As of October 2026)
Splitting one lifetime into total hours, minutes and seconds is not covered here, and no age in years is produced. Days are all this tool reports. Target counts from 1 to 200,000 days are accepted.
Frequently asked questions
Day zero. The count is the counting date minus the birth date, so entering the day of birth as the counting date returns zero days.
No. Leave it empty and you get the first person's count and target date only, with the gap row marked as not entered.
The date it was reached is still shown, and the remaining row says how many days ago it passed. Negative numbers are never printed.