Date Calculator

Date arithmetic allows you to add or subtract time periods from a date:

• Days: Exact 24-hour periods
• Weeks: 7-day periods
• Months: Calendar months (varying length)
• Quarters: 3-month periods
• Years: Calendar years (365 or 366 days)

Note: When adding months, if the target day doesn't exist (e.g., Feb 30), the last day of the month is used.

The duration calculator shows the time between two dates in multiple formats:

• Total Days: Absolute number of days
• Years/Months/Days: Human-readable breakdown
• Weeks: Useful for shorter periods
• Business Days: Excludes weekends (Saturday and Sunday)

Inclusive vs Exclusive: This calculator uses exclusive end dates (end date not counted).

Calculate exact age with precision:

• Years, Months, Days: Exact age breakdown
• Total Days: Days alive since birth
• Next Birthday: Days until next birthday
• Milestones: Special age markers

Leap Day Birthdays: If born on Feb 29, age changes on Feb 28 in non-leap years.

A year is a leap year if:

• Divisible by 4 AND
• NOT divisible by 100 OR divisible by 400

Examples:

• 2024: Leap year (divisible by 4)
• 2100: Not a leap year (divisible by 100 but not 400)
• 2000: Leap year (divisible by 400)

Common date formats around the world:

• ISO 8601: YYYY-MM-DD (international standard, sortable)
• US: MM/DD/YYYY
• European: DD/MM/YYYY
• Long: Month DD, YYYY
• RFC 2822: Used in email headers
• Unix Timestamp: Seconds since Jan 1, 1970

Business days (also called working days or weekdays) exclude:

• Saturdays
• Sundays
• Note: This calculator does not account for holidays

Calculation: Total days - (number of complete weeks × 2) - weekend days in partial weeks

Project Planning:

• Calculate project end date from start + duration
• Find number of working days in a project

Legal/Financial:

• Contract term lengths
• Statute of limitations deadlines
• Age of majority calculations

Personal:

• Days until vacation
• Anniversary calculations
• Exact age for forms