How does it calculate exact age?

The calculator determines the complete years, months, and days elapsed from your birth date to today, considering different month lengths and leap years.

Can I calculate the difference between any pair of dates?

Yes, enter any start and end date. The calculator will give you the exact difference in years, months, days, total weeks, and total hours.

How does adding or subtracting days work?

Select a start date, choose whether to add or subtract, and enter the number of days. The calculator will give you the resulting date considering months of different lengths.

Does it consider leap years?

Yes, all calculations consider leap years (every 4 years, except centuries not divisible by 400). February has 29 days in leap years.

What can I use the date calculator for?

It's useful for calculating your exact age, knowing how many days until an event, calculating work deadlines, expiration dates, pregnancy periods, or any date-related calculation.

Date Calculator | Calcufast

How Does the Date Calculator Work?

Our date calculator is a versatile tool with three calculation modes that cover the most common date and time-related needs.

Mode 1: Calculate Age from Birth Date

This mode calculates your exact age in years, months, and days. Unlike simply subtracting years, our calculator considers the different lengths of each month and leap years to give you a precise result.

Age calculation

Age = Current date - Birth date Result: X years, Y months, Z days Total days = (Difference in milliseconds) / (86,400,000 ms/day)

In addition to exact age, we show you:

Total days lived: A different perspective on your lifetime.
Total weeks: Useful for planning and curiosity.
Days until your next birthday: So you don't forget to celebrate.

Mode 2: Difference Between Two Dates

How much time is there between two events? This mode calculates the exact difference between any pair of dates, showing the result in multiple formats.

Practical uses

Ideal for calculating work deadlines, time between events, project durations, warranty periods, or simply curiosity about the time distance between two moments.

Results included:

Exact years, months, and days
Total days
Total weeks
Total hours

Mode 3: Add or Subtract Days

Need to know what date it will be in 90 days? Or what date it was 45 days ago? This mode allows you to add or remove days from any date and get the correct result.

Common applications:

Legal deadlines: "30 business days from..."
Expiration dates: "This product expires in 180 days"
Event planning: "The wedding is in 120 days"
Pregnancy: "When are 40 weeks?"

Leap Years

Leap year rule

A year is a leap year if divisible by 4, EXCEPT for years divisible by 100, UNLESS they're also divisible by 400. That's why 2000 was a leap year but 1900 wasn't. The next "centennial leap year" will be 2400.

Leap years add an extra day (February 29) every 4 years to compensate for the solar year lasting 365.2422 days, not exactly 365. This seemingly small difference would accumulate a 24-day error in a century if uncorrected.

Fun Facts About Time

One million seconds equals approximately 11.5 days.
One billion seconds equals approximately 31.7 years.
The 7-day week has Babylonian origins, based on the 7 visible celestial bodies.
The longest day of the year (summer solstice) has up to 15 hours of daylight at mid-latitudes.
The average Gregorian year lasts 365.2425 days, very close to the actual solar year.

Calendar Systems

The Gregorian calendar is the international standard, but other active systems exist:

Hebrew calendar: Lunisolar, used for Jewish holidays.
Islamic calendar: Purely lunar, 354 or 355 days per year.
Chinese calendar: Lunisolar, basis for Chinese New Year.
Persian calendar: Solar, used in Iran and Afghanistan.

Use the 'Age' mode of our calculator. Enter your birth date and you'll get not only your age in years, months, and days, but also the exact total number of days you've lived.

No, business days are typically Monday through Friday. Our calculator counts calendar days (including weekends and holidays). For business days, you'd need to subtract weekends from the result.

Yes, you can add up to 36,500 days (approximately 100 years) to any date. Note that for very distant dates, factors like calendar changes could affect precision.