BirthdayCalculator
Everything about a birthday from one date. This free Birthday Calculator reveals your birth day-of-week, runs a next birthday countdown, names your zodiac sign, lists age milestones and adds a few fun birthday statistics along the way.
Discover Your Birthday Details
Enter a date of birth to see its birthday details.
How the Birthday Calculator Works
Four quick steps to your birthday details.
Enter Birthdate
Choose the date of birth in the picker — any date from 1900 onwards.
Calculate
Press "Calculate" to get the birth day, zodiac sign and next birthday at once.
View Countdown
See the days until your next birthday and the weekday it falls on.
Explore Milestones
Get the exact dates of milestone birthdays — 18th, 21st, 30th, 50th, 75th and 100th.
What Is a Birthday Calculator?
What a birthday tool adds beyond birthday insights you already know.
Birthday analysis
A Birthday Calculator does more than work out an age. It finds the day of the week you were born, your zodiac sign, the days left until your next birthday and when your age milestones will fall.
A birthday moves to a different weekday each year — a Tuesday this year often means a Wednesday next year, or a Thursday after a leap day. The calculator works this out for any year.
Zodiac signs
The Western zodiac has 12 signs of roughly a month each, decided by birth month and day: Aries (Mar 21–Apr 19), Taurus (Apr 20–May 20), Gemini (May 21–Jun 20), continuing round to Pisces (Feb 19–Mar 20).
Milestone birthdays
Some ages carry special weight: 18 (legal adulthood in many countries), 21 (US drinking age), 30/40/50 (new decades), 65 (a common retirement age) and 100 (a centenarian). Each milestone date is listed for you.
When to Use a Birthday Calculator
Fun and practical birthday uses.
Party Planning
Check which day of the week the next birthday lands on and plan a weekend party or a weeknight dinner.
Gift Countdown
Know exactly how many days until someone's birthday so the present arrives in time.
Zodiac Curiosity
Look up the zodiac sign of friends and family — an easy conversation starter.
Age Verification
Confirm dates of legal milestones such as 18 for voting, 21 for drinking in the US or 65 for retirement.
Historical Dates
Find the weekday famous people were born on — was Lincoln born on a Sunday? Enter the date and see.
Milestone Celebrations
Plan years ahead for milestone birthdays by knowing the exact date of a 50th or 100th.
Birthday Calculation Examples
A few birthday facts, worked out.
Born on a Monday
January 15, 1996 fell on a Monday — "Monday's child is fair of face", as the old rhyme goes.
Zodiac sign
Born January 15 → ♑ Capricorn (Dec 22 – Jan 19), an earth sign associated with discipline and ambition.
Next birthday countdown
With a January 15 birthday, on June 23 there are 206 days to go, and in 2027 the birthday falls on a Friday.
100th birthday
Born in 1996 → the 100th birthday is January 15, 2096, a Sunday. Worth a note in the calendar!
Birthday Results at a Glance
A visual summary of your birthday details from the calculator above.
Your Exact Current Age
Your exact current age in years, months and days comes from comparing the date of birth with today, together with the total number of days lived, every leap day included.
Your Next Birthday
The date of your next birthday, its weekday, the days left and the age you'll turn all follow from the birthdate. If this year's birthday has passed, next year's is shown.
Birthday Countdown Visualization
The progress bar shows how far you are between your last birthday and your next birthday, and it moves as soon as you change the date of birth.
How Long Until My Birthday?
Several ways to express the time remaining until your next birthday.
Days Until My Birthday
The countdown is an exact count of calendar days from today to the birthday, not an estimate based on 30-day months. From September 26 to January 15, every remaining day of September, October, November and December is counted, then the first days of January.
Weeks Until My Birthday
The days left are divided by 7 to give complete weeks and remaining days — 111 days is 15 weeks and 6 days.
Months and Days Until My Birthday
Months are counted with calendar-based subtraction: step forward month by month from today, then count the leftover days. September 26 to January 15 is 3 months and 20 days, not a rough figure from 30-day months.
Interactive Birthday Countdown
The card shows your countdown in days, weeks and months, all from your date of birth.
When Is My Next Birthday?
Get the exact date and plan ahead.
Find Your Next Birthday Date
If your birth month and day are still ahead this year, the next birthday is this year; if they have already passed, it is next year. Either way, the date shown is always in the future.
How Old Will I Be on My Next Birthday?
Your next age is the difference between the next birthday's year and your birth year. Born in 1996 with a next birthday in 2027, you'll turn 31.
Interactive Next-Birthday Timeline
The timeline marks your last birthday, where today sits, and your next birthday, with dates and the countdown.
What Day of the Week Was I Born?
Find the exact weekday you were born on.
Find Your Birth Weekday
Every date in the Gregorian calendar has a fixed weekday. The calculator reads it straight from the actual calendar — no shortcut formulas — so the answer appears as soon as you enter your birthdate.
Interactive Weekday Calendar Visual
The visual highlights the weekday of your birth and refreshes when you change the date.
Worked Example
Someone born on January 15, 1996 was born on a Monday — "fair of face", according to the rhyme. Try your own date to find yours.
Birthday Calculator Worked Examples
Worked calculation examples for everyday cases.
Birthday Later This Year
Example Calculation
Date of Birth: November 20, 2000
Today's Date: September 26, 2026
Next Birthday: November 20, 2026 (Friday)
Days Remaining: 55
Age Turning: 26
November 20 hasn't happened yet this year, so the next birthday is in 2026.
Birthday Already Passed
Example Calculation
Date of Birth: March 10, 1995
Today's Date: September 26, 2026
Next Birthday: March 10, 2027 (Wednesday)
Days Remaining: 165
Age Turning: 32
March 10 is already behind us this year, so next year's birthday is used.
Birthday Is Today
Example Calculation
Date of Birth: September 26, 1998
Today's Date: September 26, 2026
Age Today: 28 years
Days Until Next Birthday: 365 (366 if a leap day falls in between)
On the birthday itself, the following year's birthday becomes the next one and the countdown starts again from a full year.
February 29 Birthday
Leap-Year Example
Date of Birth: February 29, 2000
In 2028 (leap year): the next birthday is February 29, 2028
In 2027 (non-leap year): the birthday moves to March 1, 2027, because there is no February 29. That is precisely how this calculator behaves — the JavaScript Date object rolls February 29 forward to March 1 in non-leap years.
How the Birthday Countdown Is Calculated
The birthday calculation logic, step by step.
Finding the Next Birthday
A date is built from the current year plus your birth month and day. If that date has passed, or is today, the following year is used instead, so the next birthday is always ahead.
Calculating Days Remaining
The gap between today and the next birthday is measured in milliseconds, divided by the 86,400,000 milliseconds in a day, and rounded up to whole calendar days.
Calculating Age on the Next Birthday
The age you'll turn is the next birthday's year minus your birth year — the number of complete years you'll have lived on that day.
Birthday Calculation Flow Diagram
The diagram walks through each stage of the birthday calculation.
February 29 Birthday Calculator
How leap-day birthdays are treated.
February 29 Birthday in a Leap Year
In a leap year — divisible by 4, except century years not divisible by 400 — February has 29 days, so a February 29 birthday happens on the day itself and February 29 is shown as the next birthday.
February 29 Birthday in a Non-Leap Year
In a non-leap year February stops at 28. Asking for February 29 makes the JavaScript Date object move to March 1, so this calculator treats March 1 as the birthday in non-leap years rather than February 28.
Interactive Leap-Year Example
The grid follows a February 29 birthday across several years, showing which are leap years and the date the birthday lands on.
Birthday Calculation Scenarios
Practical ways to put the Birthday Calculator to work.
Planning a Birthday Party
Example
A child's birthday is December 12. Checked on September 26, 2026, the calculator shows 77 days to go and a Saturday birthday — eleven weeks to book a venue, send invitations and order the cake, with no school or work to plan around.
Planning a Birthday Gift
Example
Your partner's birthday is 3 weeks and 4 days away — 25 days. With 5–7 day delivery, an online order still arrives in time; with under a week left, a local shop or a digital gift is the safer bet.
Checking a Friend or Family Member's Birthday
Example
Enter a friend's birthdate, such as July 14, 1992. Checked on September 26, 2026, their next birthday is July 14, 2027 (a Wednesday), they will turn 35, and there are 291 days to go — plenty of notice for a card or a surprise.
Birthday Milestone Timeline
An interactive view of your upcoming milestone birthdays.
Upcoming Birthday Milestones
Ages such as 18, 21, 30, 40, 50, 60, 65, 75 and 100 carry cultural, legal or personal meaning. Alongside the milestone dates in the results, this interactive timeline highlights which milestone comes next for you.
Interactive Milestone Timeline
Milestones already reached are dimmed, your next upcoming milestone glows gold, and later ones appear as normal. The timeline follows the date of birth you enter.
Birthday Calculator Quick Answers
Short answers to common birthday questions.
How many days until my birthday?
Enter your date of birth: the result is the exact number of calendar days from today to your next birthday, and it updates each day.
How many weeks until my birthday?
The days left are divided by 7 into complete weeks and leftover days — 45 days is 6 weeks and 3 days.
When is my next birthday?
You get the full date — month, day and year — and the day of the week. If this year's has gone, next year's date is shown.
What day of the week was I born?
Enter your birthdate to see the exact weekday, worked out from the Gregorian calendar for any year.
How old will I be on my next birthday?
Your birth year is subtracted from the year of your next birthday, giving the age you will turn.
What happens if my birthday has already passed this year?
Then next year's date is used automatically, and the countdown, weekday and turning age all refer to that occurrence.
How does the calculator handle February 29?
In non-leap years, a February 29 birthday moves to March 1; in leap years it stays on February 29. This mirrors how the JavaScript Date object behaves.
Birthday Calculator FAQ
Answers to common questions about the Birthday Calculator.
Enter your date of birth and the weekday appears straight away — Monday, Tuesday and so on — worked out from the Gregorian calendar.
The calculator counts the days left until your next birthday and tells you which weekday it lands on. The count updates by itself as the days pass.
From your birth month and day, using the standard Western zodiac ranges — Aries runs from March 21 to April 19, Taurus from April 20 to May 20, and so on.
Ages that are often celebrated or legally significant, such as 18, 21, 30, 40, 50, 60, 75 and 100. The calculator lists the exact date of each so you can plan early.
Yes. Enter anyone's date of birth to see the weekday they were born, their next birthday, zodiac sign and milestone dates — handy for surprise parties and gifts.
Yes. It is free, with no sign-up, and the dates you enter stay in your browser.