Date Span Calculator

Calculating the time between two dates

The calculator converts both dates to milliseconds since the Unix epoch (January 1, 1970) and finds the difference. This is then broken down into years, months, weeks, days, hours, minutes, and seconds for a complete picture.

Leap year rules

A year is a leap year if it is divisible by 4, except for years divisible by 100—unless they are also divisible by 400. So 2024 is a leap year, 1900 was not, and 2000 was. The calculator counts how many February 29ths fall within your date range.

Business day calculations

Business days are Monday through Friday, excluding weekends. The calculator iterates through each day in the range and tallies weekdays and weekends separately. Use the checkboxes to focus on business days only.

Common uses

• Project planning and deadline tracking
• Age and tenure calculations
• Contract and lease duration
• Pregnancy due date counting
• Event countdowns and reminders