Planning · Time · Calendar
Date
Calculator
Calculate days between dates, add or subtract time from any date, find your exact age, and discover what day of the week any date falls on.
—
Result
—
Weeks
Diff
Mode
Days Between Two Dates
Add or Subtract Time from a Date
Operation
Age Calculator
Day of Week Finder
Days Between
—
days
Weeks
—
Months
—
Total Days
—
Workdays
—
Weekends
—
Months
—
Breakdown
Date Calculations Made Easy
Whether you're planning a project deadline, calculating how long until an event, finding your exact age, or just curious what day of the week you were born on — this date calculator handles it all instantly.
Common Date Calculations
Days between: Count including or excluding start/end date
Workdays: Excludes Saturdays and Sundays (no holiday adjustment)
Add/Subtract: Supports days, weeks, months, years
Age: Years + months + days exact breakdown
Day of week: Uses Zeller's congruence / JS Date object
Leap year: 366 days; Feb 29 exists; divisible by 4 (not 100, or div by 400)
How many days are in each month?
January (31), February (28 or 29 in leap years), March (31), April (30), May (31), June (30), July (31), August (31), September (30), October (31), November (30), December (31). A simple way to remember: count knuckles and valleys on your fist — knuckles are 31-day months, valleys are shorter months.
What is a leap year?
A leap year occurs every 4 years and has 366 days (Feb 29 is added). Rule: divisible by 4 AND (not divisible by 100, OR divisible by 400). So 2000 was a leap year (divisible by 400), 1900 was not (divisible by 100 but not 400), 2024 is a leap year (divisible by 4, not 100). The next leap years are 2028, 2032, 2036, and 2040.
How do you count business days between dates?
This calculator counts weekdays (Monday–Friday) as workdays, excluding Saturdays and Sundays. It does NOT account for public holidays, which vary by country and region. For example, from Monday Jan 1 to Friday Jan 5: 5 calendar days, 4 workdays (assuming Jan 1 is a holiday in your country, adjust manually). For precise business-day calculations with holidays, check your specific country's official holiday calendar.
What day of the week was I born?
Use the "Day of Week" tab and enter your birthday. The day is calculated from the date alone — no need to know the year's calendar. Interesting historical facts: The moon landing (July 20, 1969) was a Sunday. September 11, 2001 was a Tuesday. January 1, 2000 was a Saturday. The most common birthday in the US is September 9 (9 months after Christmas/New Year).