Date Calculator

Calculate the difference between two dates or add/subtract days from a date.

Date Difference
Calculate between dates
Add to Date
Add time to a date
Subtract from Date
Subtract time from a date

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Understanding Date Calculations

Date calculation determines the difference between two dates or calculates new dates by adding or subtracting time periods. This tool provides precise measurements in multiple units including years, months, weeks, days, hours, and minutes, along with weekday and weekend breakdowns.

Unit Type Unit Name Value in Days
Time Unit Second 1/86,400 of a day
Time Unit Minute 60 seconds
Time Unit Hour 60 minutes = 3,600 seconds
Time Unit Day 24 hours = 1,440 minutes
Time Unit Week 7 days
Time Unit Month (avg) ~30.44 days (365.25 ÷ 12)
Time Unit Year (avg) 365.25 days (includes leap years)
Calendar Type Gregorian Calendar Most widely used calendar system
Calendar Type Julian Calendar Predecessor to Gregorian
Calendar Type Lunar Calendar Based on moon phases (~354 days)
Leap Year Rule Divisible by 4 Leap year (e.g., 2024)
Leap Year Rule Divisible by 100 Not a leap year (e.g., 1900)
Leap Year Rule Divisible by 400 Leap year exception (e.g., 2000)
Leap Year Regular Year 365 days
Leap Year Leap Year 366 days (adds Feb 29)
Day Types Weekdays Monday through Friday (5 days)
Day Types Weekend Saturday and Sunday (2 days)
Day Types Business Days Excludes weekends and holidays
Month Lengths January 31 days
Month Lengths February 28 days (29 in leap year)
Month Lengths March 31 days
Month Lengths April 30 days
Month Lengths May 31 days
Month Lengths June 30 days
Month Lengths July 31 days
Month Lengths August 31 days
Month Lengths September 30 days
Month Lengths October 31 days
Month Lengths November 30 days
Month Lengths December 31 days
Common Calculations Age Calculation Current date minus birth date
Common Calculations Project Duration End date minus start date
Common Calculations Due Date Start date plus duration
Common Calculations Deadline Target date minus current date
Common Calculations Anniversary Event date plus years
Business Use Project Planning Calculate project timelines
Business Use Contract Duration Calculate agreement periods
Business Use Payment Terms Net 30, Net 60 calculations
Business Use Leave Planning Vacation and holiday calculations
Personal Use Event Planning Wedding, birthday countdowns
Personal Use Pregnancy 280 days from last period
Personal Use Fitness Goals 90-day challenge tracking
Personal Use Relationship Dating anniversary calculations

Conversion Tip

Date calculators determine the exact difference between dates or calculate new dates by adding/subtracting time periods. They help with project planning, deadline tracking, event countdowns, and understanding time durations in multiple units including weekdays and weekends.

Quick Reference

  • Date difference = End Date - Start Date
  • Future date = Start Date + Time Period
  • Past date = Start Date - Time Period
  • Business days exclude weekends and holidays
  • Pregnancy due date: ~280 days (40 weeks) from last period
  • Standard project quarter: ~90-92 days (3 months)
  • Payment terms: Net 30 = 30 days from invoice date
  • The Gregorian calendar was adopted in 1582
  • Time zones can affect date calculations across regions
  • 1 day = 24 hours = 1,440 minutes = 86,400 seconds
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