Days until my birthday
The countdown runs from today to your next birthday. If today is your birthday it shows zero rather than 365. The day itself counts as arrived, not as a full year away. The largest figure it can ever show is 365, on the day after your birthday in a stretch that contains a 29 February.
How to count down to your birthday
The zero-on-the-day behaviour is a deliberate choice and not every calculator makes it. Treating the birthday as "already here" matches how people talk; nobody says they have 365 days to wait on their birthday. The alternative, rolling straight to next year, is defensible for a scheduling tool and wrong for a countdown. Two smaller points are worth knowing. The count is in whole calendar dates rather than 24-hour blocks, so daylight saving cannot touch it: a countdown in hours is genuinely an hour out for part of the year, and this one never is. And a 29 February birth date has no anniversary in three years out of four, so it clamps to 28 February; a leapling’s countdown still reaches zero every year, just not always on the date they were actually born.
Questions
Enter your birth date — the count runs from today.
Zero. The birthday has arrived rather than being a year away.
365, on the day after your birthday when a 29 February falls in the year ahead. Otherwise the day after is 364.
Yes, including 29 February birth dates, which clamp to 28 February in common years.
No. It counts dates rather than hours, so a clock going forward or back adds nothing and removes nothing.
It uses today as of when the page loaded, taken from your own device. Reload the next day.
Yes — enter their date instead. Only the day and month affect the countdown.