Birthday Calculator — Age, Days Lived & Zodiac Sign
Enter your birth year, month and day to instantly see your exact age in years, months and days; the total number of days you have lived; your Western zodiac sign; the weekday you were born on; and how many days until your next birthday.
36 years, 0 months, 28 days
How does this calculator work?
Enter birth year, month and day. The calculator computes exact age in years/months/days, total days lived, Western zodiac sign (tropical), the weekday born, and the countdown to the next birthday. All arithmetic uses JavaScript Date objects with the proleptic Gregorian calendar.
Formula
How this is calculated
The calculator subtracts your birthdate from today's date using calendar arithmetic. Whole years are counted first, then remaining months (borrowing days from the previous month when the current day of month is earlier than the birth day), then the leftover days within the partial month. This gives the precise breakdown used in official age reckoning worldwide.
The total days-lived figure is the integer number of whole days between the birthdate and today (computed as the millisecond difference divided by 86 400 000, floored). Zodiac signs are assigned by the tropical Western zodiac: Aries 21 March–19 April, Taurus 20 April–20 May … Pisces 19 February–20 March, with Capricorn spanning the year boundary (22 December–19 January). The weekday is read from JavaScript's Date object, which uses the proleptic Gregorian calendar.
The next-birthday countdown finds the occurrence of your birth month/day in the current calendar year; if it has already passed, it advances to the following year. The progress bar shows what fraction of the current birthday year — from your last birthday to your next — has elapsed. For 29 February birthdays in non-leap years, 28 February is used as the effective date for countdown and progress calculations.
Frequently asked questions
Age is computed by counting full calendar years first, then counting the remaining months (adjusting when the current day of month is less than the birth day, by borrowing a month), then counting the leftover days in the partial month. This matches the civil age used on passports and official documents — it is not a simple division by 365.25.
The days-lived figure is the integer count of complete 24-hour periods between your birthdate and today. It equals the total millisecond difference divided by 86 400 000, rounded down. Leap years are automatically included: a leap year contributes 366 days to the count rather than 365.
For the purpose of the countdown and the progress bar, the calculator uses 28 February in non-leap years. The "days lived" total is always accurate because it counts raw calendar days. In leap years, 29 February is used exactly as entered.
Also known as
TG we-Calculate Editorial Team. (2026). Birthday Calculator — Age, Days Lived & Zodiac Sign [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/birthday-calculator
TG we-Calculate Editorial Team. "Birthday Calculator — Age, Days Lived & Zodiac Sign." TG we-Calculate. 2026. https://we-calculate.com/calculator/birthday-calculator.
TG we-Calculate Editorial Team, "Birthday Calculator — Age, Days Lived & Zodiac Sign," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/birthday-calculator
@misc{wecalculate_birthday_calculator, title = {Birthday Calculator — Age, Days Lived & Zodiac Sign}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/birthday-calculator}}, year = {2026}, note = {TG we-Calculate} }
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