Julian Day Converter Skill

Overview

Perfect for astronomical calculations, historical date research, and applications that need a continuous day count across calendar systems.

Live Test Julian Day Converter Skill Skill →

The tool

Once your client is connected to the VerveKit server, this appears in its tool list as JulianDayConverterSkill. It is read-only and open-world — it fetches and never mutates anything on your side — so most clients call it without asking you to confirm.

Tool call

{
  "name": "JulianDayConverterSkill",
  "arguments": {
    "date": "2024-03-15"
  }
}

You do not name the tool yourself; the model picks it. Asking about 2024-03-15 in the terms this skill covers is enough for it to reach for JulianDayConverterSkill on its own — naming it explicitly also works, and is the way to force the call.

Connecting

One server URL covers every skill in the catalog, including this one. Authorization is OAuth: the client opens a browser once, and there is no key to paste into a config file.

{
  "mcpServers": {
    "vervekit": {
      "url": "https://api.vervekit.com/v1/mcp"
    }
  }
}

Per-client setup — Claude, Cursor, VS Code, ChatGPT — is on the MCP setup page.

Arguments

These are the properties on the tool's inputSchema, so a well-behaved client validates them before the call is made. Premium arguments are accepted on every plan but only take effect on plans that include them.

Argument	Type	Description
`date`Required	string	The Gregorian date in YYYY-MM-DD format date

What the model gets back

The result carries a structuredContent object matching the tool's declared outputSchema, so a client reads fields without parsing prose. status is "ok" and error is null on success; a null field means the value was not available for that input, not that the call failed.

Result

{
  "status": "ok",
  "error": null,
  "data": {
    "gregorian": "2024-03-15",
    "julianDayNumber": 2460385,
    "modifiedJulianDate": 60384.5,
    "dayOfWeek": "Friday",
    "weekNumber": 11,
    "dayOfYear": 75,
    "daysFromToday": -340
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Field	Type	Example	Description
`gregorian`	string	`2024-03-15`	The equivalent Gregorian calendar date
`julianDayNumber`	number	`2460385`	Days elapsed since noon on 1 January 4713 BC
`modifiedJulianDate`	number	`60384.5`	Julian day number shifted to start at midnight on 17 November 1858
`dayOfWeek`	string	`Friday`	Day of the week the date falls on
`weekNumber`	number	`11`	ISO week number (1-53)
`dayOfYear`	number	`75`	Day of the year (1-366)
`daysFromToday`Premium	number	`-340`	Number of days from today (negative = past, positive = future)

Failure modes

Errors come back as tool errors carrying a sentence the model can act on, not a bare status code. Error handling covers the full list.

Status	What it means
`400` / `422`	The arguments did not validate. The message names the offending one.
`401`	The OAuth session is invalid or expired — reconnect the server.
`403`	Blocked by a key restriction or an IP allow-list. Never a bad identity.
`404`	This skill is not part of VerveKit. Check the catalog.
`429`	Out of credits, or a brief rate limit. The message tells them apart.

A call costs 2 credits each time the tool actually runs; a model that reasons about the tool without calling it costs nothing.

Use cases

Astronomical Software: Calculate precise day numbers for celestial events
Historical Research: Convert historical dates to a unified day count
Date Arithmetic: Calculate day differences across long time spans
Scientific Applications: Use continuous day counts for time series data

Other ways to use Julian Day Converter Skill

Set up Julian Day Converter Skill on VerveKit, or reach the same source a different way. Your VerveKit account and credits work on all of them — one key, one balance.

Call it as a REST APIOne HTTPS endpoint and an x-api-key header, with SDKs for Node, Python and .NET.APIVerve →Reference →

Google Sheets or ExcelA =VERVE() formula fills a column — no script, no export, recalculates in place.VerveSheets →Reference →

Ground an agent on itA cited, machine-checkable fact your model can't produce on its own.VerveContext →Reference →