日期计算器

How to Calculate Days Between Two Dates

The simplest way to find days between dates is to convert both dates to a day count from a fixed reference point, then subtract. Our calculator does this automatically for any pair of dates.

Common uses for date calculations: counting days until a deadline or event, calculating someone's age in days, determining contract durations, figuring out when a payment is due, and calculating how many shopping days until a holiday.

Adding months is trickier than adding days because months have different lengths. Adding 1 month to January 31 is ambiguous — some systems use February 28, others use the last day of the target month. Our calculator uses the standard approach of adjusting to the last valid day of the month.

Useful Date Facts

• A regular year has 365 days; a leap year has 366 days
• Leap years occur every 4 years, except centuries not divisible by 400 (2000 was a leap year; 1900 was not)
• There are 52 weeks + 1 day in a regular year; 52 weeks + 2 days in a leap year
• The average month length is 30.44 days (365.25 ÷ 12)

常见问题

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