Date Calculator
Run reliable date math with leap-year and month-end aware behavior.
Your calculation is performed locally in your browser.
Results are estimates for informational purposes and should not be treated as financial, tax, or investment advice.
Date Difference
0 years, 0 months, 0 days
Total days: 0 | Total weeks: 0.00
Date Add/Subtract
Result date: 2026-10-23
Use in code
Reliable date math uses calendar functions and explicit month-end handling.
Add months safely
TypeScriptPrimary API
setUTCMonth(currentMonth + amount)
Clamps month-end dates to valid day ranges.
Built-in API
function addMonths(date: Date, amount: number) {
const copy = new Date(date);
copy.setUTCMonth(copy.getUTCMonth() + amount);
return copy;
}How this calculator works
- Use Date Difference to compare two dates.
- Use Add/Subtract to shift a date by days, weeks, months, or years.
- Review both component differences and total days/weeks.
Use cases
- Plan deadlines and contract durations.
- Compare inclusive and exclusive day counting clearly.
Limitations and assumptions
- Calculations operate on date-only values rather than clock time.
- Inclusive counting is optional and clearly labeled.