Date Calculator
Calculate exact calendar days and working business days between two dates, or project future dates by adding or subtracting days.
About the Date Calculator
The Date Calculator solves common calendar queries: finding how many days remain between two specific dates, or determining what date occurs a given number of days, weeks, or months into the future or past.
Unlike simple calendar counting, this tool accurately reflects month-end boundary variations, leap years, and separates standard weekend days from Monday-through-Friday business working days—essential for project planning, legal deadlines, notice periods, and event countdowns.
How to Calculate Date
Choose Mode: "Days Between Dates" or "Add / Subtract Days".
For Date Difference: Select your Start Date and End Date.
Check "Include End Day" if your timeline requires inclusive boundary counting.
View total days, weeks, remaining days, and Monday-to-Friday business days.
Date Duration Math
Total Days = (End Date (ms) - Start Date (ms)) / (1000 × 60 × 60 × 24) Weeks = ⌊Total Days / 7⌋ Remaining Days = Total Days mod 7
Calculates the epoch timestamp delta between midnight UTC timestamps and counts intervening Monday-through-Friday days for business intervals.
Variable Descriptions
- Start Date
- The reference beginning date
- End Date
- The target completion date
- Business Days
- Count of weekdays (Monday through Friday) excluding weekends
Worked Example
Important Considerations & Tips
- Standard date difference calculates full days elapsed between two dates.
- Leap years are automatically factored in (2028, 2032, etc. have 29 days in February).
- Business day counts do not include official national public holidays as those vary by country.
Frequently Asked Questions
Does the date calculator count both the start date and end date?
By default, the calculator counts the interval from the start date up to the end date (elapsed time). You can toggle "Include end day" to include both boundary days.
How are business days defined?
Business days represent Monday through Friday. Saturdays and Sundays are excluded as weekend days.
Can I add business days only?
The addition tool adds calendar days; to calculate business day project deliverables, factor in 2 weekend days per 5 business days.
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