Date Calculator
Date Interval
Total Days0 Days
Before/After Date
Before2026-09-27
After2026-09-27
Date Calculator — Add/Subtract Time & Calculate Date Difference
Date Calculator helps you add or subtract days, weeks, months, and years from any date, or calculate the exact difference between two dates. Pick a base date, adjust the value, and get the result instantly — including total days with an optional include-start-date toggle.
Features & Usage Tips
Add or subtract days, weeks, months, or years from a date, or count the exact days between two dates — all computed instantly in your browser.
How Date Arithmetic Works
Date arithmetic looks simple but has subtle rules: adding a month to January 31 rolls over to the end of February, and difference calculations may include or exclude the start date depending on your convention. This tool handles both cases explicitly.
- Add / Subtract Mode: Start from today or any custom date, then add or subtract days, weeks, months, or years; the resulting date is shown immediately.
- Difference Mode: Pick two dates and get the total days, weeks, months, and years between them.
- Include Start Date: Toggle whether the start date counts toward the total — useful for contract or billing day counts.
Use Cases
📅 Deadline Planning: Calculate project milestones — 45 days from kickoff, or 3 months from today.
📋 Contract & Billing: Count the exact days between two dates (with or without the start date) for prorated billing.
🧑🍼 Age & Tenure: Find the precise age in years, months, and days from a birth date.
🌍 Travel & Logistics: Work out arrival dates across time zones or the duration of a trip.
Privacy & Security
This tool runs entirely in your browser. All date calculations are performed locally on your device — no data is sent to any server.