🎂 Pet Birthday Countdown Calculator

Enter your pet's birth date to see their exact age and a countdown to their next birthday.

Pet's Birth Date

How the age and the countdown are worked out

Both figures come off one date, compared against local midnight today:

age in days   = floor((today - birth) / 86,400,000 ms)
age in years  = calendar years, less 1 if the day has not come round yet
next birthday = this year's day and month, +1 year if it has passed
days until    = round((next birthday - today) / 86,400,000 ms)

A pet born on 1 May 2022 turns 4 on 1 May 2026; ask on 20 April that year and the countdown reads 11 days. The years figure steps up only on the birthday itself, so it never rounds a pet up early, and the day count beside it keeps climbing - seven years is about 2,557 days, leap days included.

Using it

On the birthday itself the countdown reads 0, not 365. The tool only rolls to next year once the date has actually passed.
A future date is rejected rather than shown as a negative age.
29 February birthdays land on 1 March in non-leap years, since the date rolls forward rather than skipping to 2028.
The printed next-birthday date is formatted in UTC. East of Greenwich it can show the day before; the days-until count is still right.

Shelter and rescue pets usually carry an estimated birth date, often set from a vet's read of the teeth, so the arithmetic here is exact on a date that may not be. Many people adopt the intake date as a "gotcha day" instead, which has the advantage of being certain.

Frequently asked questions

How many days until my dog's birthday?

Enter the birth date and the tool counts whole days from today to the next time that day and month come round. It shows 0 on the day, and the maximum it can show is 365, or 366 across a leap year.

What if my pet was born on 29 February?

The countdown targets 1 March in years without a 29 February, so the birthday is marked every year rather than once in four.

I do not know my rescue's exact birthday - what should I enter?

Use the shelter's estimate, or the adoption date if there is none. The age in years is then approximate, but the countdown still gives you a fixed date to work to.