Add/subtract to a date | Calculate Date Changes Effortlessly
Calculate new dates by adding or subtracting days, months, or years. Input a starting date and adjustment amount for immediate results.
What Is an Add/Subtract Date Calculator?
An add or subtract date calculator finds a new date by adding or removing a number of days, weeks, months or years from a start date. It handles month lengths and leap years for you — great for deadlines, due dates and reminders.
What Is an Add/Subtract Date Calculator?
An add or subtract date calculator finds a new date by adding or removing a number of days, weeks, months or years from a start date. It handles month lengths and leap years for you — great for deadlines, due dates and reminders.
How to Use the Date Calculator
1. Select your starting date and time
2. Choose whether to add or subtract time periods
3. Enter values for years, months, weeks, days, hours, minutes, or seconds
4. Click Calculate to see the result
Key Features
- Calculate future and past dates with precision
- Support for multiple time units
- Instant calculations with real-time validation
- Copy results with one click
Common Use Cases
- Project deadline planning
- Contract term calculations
- Event planning and scheduling
- Age calculations
Use this tool from your AI agent
Free JSON API and Model Context Protocol (MCP) server. No signup, no API key, CORS open. Designed for Claude, ChatGPT, Cursor, scripts and frontend apps.
curl -X POST https://mate.tools/api/v1/date-math.php \
-H "Content-Type: application/json" \
-d '{"start":"2026-05-10","add":"+90 days"}'import urllib.request, json
req = urllib.request.Request(
"https://mate.tools/api/v1/date-math.php",
data=json.dumps({"start":"2026-05-10","add":"+90 days"}).encode(),
headers={"Content-Type": "application/json"},
)
with urllib.request.urlopen(req) as r:
print(json.load(r))const r = await fetch("https://mate.tools/api/v1/date-math.php", {
method: "POST",
headers: { "Content-Type": "application/json" },
body: JSON.stringify({"start":"2026-05-10","add":"+90 days"}),
});
console.log(await r.json()); Add to claude_desktop_config.json (Claude Desktop), ~/.cursor/mcp.json (Cursor), or any other MCP-compatible client:
{
"mcpServers": {
"mate-tools": {
"command": "npx",
"args": ["-y", "@mate-tools/mcp-server"]
}
}
}Frequently Asked Questions
Select today as your starting date, choose "Add," enter 90 in the Days field, and click Calculate. The tool will instantly show you the exact date 90 days in the future.
Yes, you can fill in values for years, months, weeks, days, hours, minutes, and seconds simultaneously. The calculator will apply all of them in a single calculation.
Yes, the calculator correctly handles leap years. When adding or subtracting time periods that cross February 29, the result will accurately reflect whether the target year is a leap year.
