Date Calculator
Calculate date differences or add/subtract days, weeks, months, years
Overview
Our online date calculator provides convenient date difference and date arithmetic functions. Quickly calculate the number of days between two dates, or add/subtract days, weeks, months, and years from a given date. Supports business day mode that automatically excludes weekends. Accurately handles leap years, ideal for project scheduling, countdowns, tenure calculations, and more.
Features
- Calculate days between two dates
- Add/subtract days/weeks/months/years
- Business day calculation (excluding weekends)
- Precise day-level calculation
- One-click copy result date
- Gregorian and lunar calendar reference
- Automatic leap year detection
How It Works
- Choose a calculation mode: date difference or date arithmetic
- In date difference mode, select a start date and an end date
- In add/subtract mode, enter a base date, amount, and time unit
- View the result with one-click copy support
Tips
- For project durations, use date difference to find total days, then use add/subtract to calculate the deadline
- When setting reminders or countdowns, use add/subtract to calculate the target date from today
- Note that leap years have 29 days in February — the tool handles this automatically
FAQ
Does the date difference include the start date?
The result represents the number of natural days between two dates. For example, January 1 to January 3 shows 2 days. If you need to include both the start and end dates, add 1 to the result.
What happens when adding months results in a non-existent date?
When adding or subtracting months results in an invalid date (e.g., January 31 + 1 month), the result automatically adjusts to the last day of that month. For example, January 31 + 1 month gives February 28 (common year) or February 29 (leap year).
Does the tool handle time zones?
Calculations are based on the local time zone. For cross-timezone date calculations, it is recommended to convert all dates to the same time zone first to ensure accurate results.