Date Difference Calculator
Calculate the number of days, weeks, months, and years between two dates.
Counting Days Between Any Two Dates
Whether you are figuring out how many days until a vacation, how long a project has been running, when a contract expires, or how many days since a significant event, this calculator gives you the answer in multiple units simultaneously — days, weeks, months, and years. It handles leap years, variable month lengths, and any date range correctly without any manual counting.
Business Days vs. Calendar Days
Calendar days count every day including weekends and holidays. Business days (also called working days) count only Monday through Friday, excluding weekends. Many legal deadlines, contract terms, and payment due dates are expressed in business days. A 10-business-day deadline is 14 calendar days if no holidays fall within that period. When precision matters — for legal or financial purposes — always clarify whether the stated days are calendar or business days.
Common Uses for Date Difference Calculations
Project management: calculating how many days remain until a deadline or how long a phase has taken. Finance: determining exact day counts for interest calculations, since daily interest accrues on calendar days. Legal: measuring statute of limitations periods, notice periods, and contract durations. Personal: counting down to a wedding, a vacation, a due date, or a birthday. And genealogy: calculating ages and time spans from historical records where calendar arithmetic quickly becomes tedious by hand.
Frequently Asked Questions
How many days are in a year?
A common year has 365 days. A leap year has 366. Leap years occur every 4 years (divisible by 4), except for century years, which must be divisible by 400.