Date Calculator
Calculate exact differences between two dates, or add and subtract business days, weeks, and months.
Exact Time Difference
3 months, 0 days
91Days
13Weeks
3Months
2,184Hours
Online Date Calculator — Days Between Dates & Date Math
Calculate exact days between two calendar dates, or add and subtract business days, weeks, and months from any target date.
How to Use This Tool
- 1To calculate days between dates: Select your start date and end date.
- 2Review the exact breakdown in years, months, weeks, days, and total hours.
- 3To add or subtract time: Switch to the "Add / Subtract" tab, choose your base date, and enter the numbers of days, weeks, or months.
Key Features & Capabilities
Calendar Accuracy
Accounts for differing month lengths (28, 30, 31 days) and leap years.
Multi-Unit Breakdown
Provides simultaneous outputs in total days, weeks, months, and hours.
Bidirectional Date Math
Add or subtract past and future periods with instant re-calculation.
Popular Use Cases
Legal & Contract Deadlines
Calculate notice periods (e.g., 30-day, 60-day, 90-day contract milestones).
Pregnancy & Due Dates
Calculate gestational weeks and trimester date markers.
Project Sprints
Determine working days and milestone completion targets.
Frequently Asked Questions (FAQ)
Does this calculator handle leap years?
Yes. AlarmOnline.net date calculation strictly adheres to Gregorian calendar standards and correctly handles leap day (February 29) occurrences.