Day calculation — free day & date calculators
Welcome to Day CPU — your hub for fast and accurate day calculation. Find out how many days between dates, add or subtract days from today, jump weeks ahead, or discover the weekday you were born. All calculators are free and simple to use.
Quick day calculation tool
Result
Select two dates to calculate the difference…
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Days from today
Add or subtract any number of days from a start date and get the result date and weekday.
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Days between dates
Enter two dates to calculate the exact number of days, weeks, and months in between.
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How old am I calculator
Enter your birth date to see your exact age in years, months, days — plus total hours, minutes, and seconds.
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What weekday was I born?
Instantly find the weekday you were born and your next birthday weekday.
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Weeks from now
Quick access to 1–20 weeks from today calculators. Jump by whole weeks and keep the weekday consistent.
What is day calculation?
Day calculation is the process of working with calendar dates: adding or subtracting days, counting the difference between two dates, or converting dates into weeks, months, or weekdays. Our calculators make this easy — no need for manual counting or remembering leap years.
Use cases include planning trips, setting deadlines, checking age precisely, or satisfying curiosity like “What day will it be 100 days from now?”
Day calculation — FAQs
What is a day calculation?
It means computing with dates — like adding days to today, finding days between dates, or checking what weekday a date falls on.
Do these tools include weekends and leap years?
Yes. All our calculators use the modern Gregorian calendar, handling month lengths and leap years automatically. Weekends are included because we count calendar days.
Can I calculate weeks or months too?
Yes. “Weeks from now” calculators add whole weeks, and the “Days between dates” tool also shows approximate months.
Is this free?
Yes. All day calculation tools on Day CPU are 100% free to use.
Why use Day CPU?
We focus on simplicity, speed, and accuracy. All tools run in your browser, so results appear instantly. We also explain the formulas used — so you always know how your result is calculated.