Utilities
Convert any date to its day-of-year number (1-366) and back, with ISO week number, leap-year check, and days remaining in the year.
Call this tool from your code in three languages.
curl -X POST 'https://api.elysiatools.com/en/api/tools/day-of-year-converter' \
-H 'Content-Type: application/json' \
-d '{"mode":"date-to-doy","date":"2026-07-04","year":2026,"dayNumber":0}'Send a POST request with your inputs as JSON. File parameters require a separate upload first.
POST https://api.elysiatools.com/en/api/tools/day-of-year-converter| Name | Type | Required | Description |
|---|---|---|---|
| mode | select | Yes | — |
| date | date | No | — |
| year | number | No | — |
| dayNumber | number | No | — |
Text result
{
"result": "Processed text content",
"error": "Error message (optional)",
"message": "Notification message (optional)",
"metadata": {
"key": "value"
}
}Add this tool to your Model Context Protocol server so AI agents can list and call it.
Add this block to your MCP client configuration:
{
"mcpServers": {
"elysiatools-day-of-year-converter": {
"name": "day-of-year-converter",
"description": "Convert any date to its day-of-year number (1-366) and back, with ISO week number, leap-year check, and days remaining in the year.",
"baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=day-of-year-converter",
"command": "",
"args": [],
"env": {},
"isActive": true,
"type": "sse"
}
}
}After connecting to the SSE endpoint, list the exposed tools:
{
"jsonrpc": "2.0",
"id": 1,
"method": "tools/list"
}Invoke the tool by its id, passing arguments built from its parameters:
{
"jsonrpc": "2.0",
"id": 2,
"method": "tools/call",
"params": {
"name": "day-of-year-converter",
"arguments": {
"mode": "date-to-doy",
"date": "2026-07-04",
"year": 2026,
"dayNumber": 0
}
}
}Questions or issues? Contact [email protected]