Birthday Calculator — Countdown, Zodiac Sign & Day of Week
This birthday calculator finds exactly how many days remain until your next birthday, what day of the week you were born, your western zodiac sign, how old you will turn, and how many total days you have been alive. Enter your birth date below for instant results.
Birthday Calculator
Enter your birth date to find out how many days until your next birthday, your zodiac sign, the day of the week you were born, and more.
Frequently Asked Questions
How do I calculate days until my next birthday?
To calculate days until your next birthday, find the date of your next birthday (this year or next year if your birthday has already passed), then subtract today's date. The result in days is your countdown. Our calculator does this automatically — just enter your birth date.
What day of the week was I born on?
Enter your birth date into the birthday calculator above to find out what day of the week you were born on. For example, January 1, 2000 was a Saturday. The day of the week is determined using the Gregorian calendar.
What is my zodiac sign?
Your zodiac sign is determined by your birth month and day. Aries runs March 21 – April 19, Taurus April 20 – May 20, Gemini May 21 – June 20, Cancer June 21 – July 22, Leo July 23 – August 22, Virgo August 23 – September 22, Libra September 23 – October 22, Scorpio October 23 – November 21, Sagittarius November 22 – December 21, Capricorn December 22 – January 19, Aquarius January 20 – February 18, and Pisces February 19 – March 20.
How many days have I been alive?
To calculate how many days you have been alive, subtract your birth date from today's date and convert the result to days. Every 4 years you accumulate an extra day due to leap years. A person born on January 1, 2000 has been alive for approximately 9,584 days as of March 2026. Enter your exact birth date above to get your precise count.
What happens if my birthday is February 29 (leap day)?
People born on February 29 — called leaplings — only have a technical birthday every 4 years. In non-leap years, this calculator advances the date to March 1 (consistent with JavaScript's date handling). Most countries treat either February 28 or March 1 as the legal birthday in non-leap years.
How do I calculate what day of the week my next birthday falls on?
This birthday calculator automatically shows you what day of the week your next birthday falls on. Simply enter your birth date and the calculator determines your next birthday date and looks up the corresponding day of the week.
How is the next birthday age calculated?
The next age is calculated by subtracting your birth year from the year of your next birthday. For example, if you were born in 1990 and your next birthday is in 2027, you will turn 37 (2027 − 1990 = 37).
What is the most common birthday?
According to US birth records, September 9 is the most common birthday, followed by other mid-September dates. Births peak from July through early October. The least common birthday is February 29 (occurs only in leap years), followed by December 25 and January 1, when fewer births are scheduled.
How Birthday Calculations Work
How Birthday Calculations Work
A birthday calculator determines several key facts from a given birth date. Here is how each value is computed:
Days Until Next Birthday
The calculator takes today's date and constructs the next occurrence of your birth month and day. If that date has already passed this calendar year, it advances to the following year. The difference in milliseconds is then divided by 86,400,000 (milliseconds per day) and rounded up with Math.ceil() to get the number of whole days remaining.
Next Age
The next age is simply the year of the upcoming birthday minus the birth year. For example, if you were born in 1990 and your next birthday falls in 2027, you will turn 37.
Day of Week
JavaScript's Date.getDay() returns a number 0–6 (Sunday through Saturday). This index is used to look up the weekday name for both the birth date and the next birthday date.
Total Days Alive
The difference between today and the birth date in milliseconds is divided by 86,400,000 and floored to give the total number of complete days lived. This count automatically accounts for leap years because it works directly in milliseconds.
Zodiac Signs Date Table
Western astrology divides the year into 12 signs based on the position of the sun at the time of birth. Each sign corresponds to a date range:
| Sign | Symbol | Date Range | Element |
|---|---|---|---|
| Aries | ♈ | Mar 21 – Apr 19 | Fire |
| Taurus | ♉ | Apr 20 – May 20 | Earth |
| Gemini | ♊ | May 21 – Jun 20 | Air |
| Cancer | ♋ | Jun 21 – Jul 22 | Water |
| Leo | ♌ | Jul 23 – Aug 22 | Fire |
| Virgo | ♍ | Aug 23 – Sep 22 | Earth |
| Libra | ♎ | Sep 23 – Oct 22 | Air |
| Scorpio | ♏ | Oct 23 – Nov 21 | Water |
| Sagittarius | ♐ | Nov 22 – Dec 21 | Fire |
| Capricorn | ♑ | Dec 22 – Jan 19 | Earth |
| Aquarius | ♒ | Jan 20 – Feb 18 | Air |
| Pisces | ♓ | Feb 19 – Mar 20 | Water |
Exact cusp dates can shift by one day depending on the year due to leap years and the precise moment the sun enters each sign.
Leap Year Birthdays (February 29)
People born on February 29 — known as "leaplings" or "leap day babies" — only have a true birthday every four years. This creates some interesting edge cases:
Legal and Official Age
Most countries treat February 28 or March 1 as the legal birthday in non-leap years. The UK and Hong Kong use March 1; many US states use February 28. This affects when a leapling reaches legal milestones such as voting age or driving age.
How This Calculator Handles Feb 29
This birthday calculator uses the calendar date as entered. In non-leap years, JavaScript automatically resolves new Date(year, 1, 29) to March 1, so the next birthday shown will fall on March 1 in non-leap years. The day-count and next-age calculations remain accurate.
How Common Are Feb 29 Birthdays?
The odds of being born on February 29 are approximately 1 in 1,461 (roughly 0.068%). There are an estimated 5 million leaplings worldwide. The Anthony, Texas and Aurora, Illinois towns in the US hold annual leap day celebrations for leap day birthdays.
Birthday Facts & Statistics
Most and Least Common Birthdays
According to US birth records, the most common birthday is September 9, followed closely by other dates in mid-September. Births peak from July through early October, roughly nine months after the holiday season. The least common birthday is February 29 (occurring only in leap years), followed by December 25 and January 1.
The Birthday Paradox
In a group of just 23 people, there is a greater than 50% probability that two people share the same birthday. With 70 people, this probability rises to 99.9%. This counterintuitive result is known as the birthday problem or birthday paradox, and it arises because the number of pairs grows quadratically with group size.
Notable Day Milestones
| Days Alive | Approximate Age |
|---|---|
| 1,000 days | ~2 years, 8 months |
| 5,000 days | ~13 years, 8 months |
| 10,000 days | ~27 years, 5 months |
| 1 billion seconds | ~31 years, 8 months |
| 15,000 days | ~41 years, 1 month |
| 20,000 days | ~54 years, 9 months |
What Day Were Most People Born On?
Tuesday is statistically the most common day of the week for births in the United States, followed by Monday and Wednesday. Saturday and Sunday have significantly fewer births because fewer elective inductions and C-sections are scheduled on weekends.