Does the tool account for leap years?
Yes. It uses native JavaScript date math, so leap days are included automatically when a range spans February 29.
Step-by-step walkthrough
Date Calculator Guide
Use this companion guide beside the interactive calculator to make sure you understand the “why” behind every click. Each section includes the classroom explanation, student-friendly language, and quick practice prompts.
Before you start
Collect the data points listed below and double-check their units. Keeping an organized “givens” list is one of the fastest ways to reduce math errors and impress exam graders.
- date math
- calendar
Detailed procedure
Step 1
Choose the mode: difference, add days, or subtract days.
Step 2
Fill in the start date and either the end date or number of days depending on the mode.
Step 3
Check the results for total days, weekly equivalent, or the resulting calendar date.
Teaching & troubleshooting tips
Can I add business days only?
This calculator works with calendar days. For business-day schedules, convert your target into calendar days before using the tool.