ISO date days in month

iso-date-days-in-month · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

Return the number of calendar days in a given proleptic Gregorian year and month.

Use when you need to: iso date days in month · days in a calendar month · month length.

Supported

• iso date days in month
• days in a calendar month
• month length

Not supported

• fiscal months
• Julian calendar
• timezones

Behavior

• year is a JSON integer 1-9999. month is a JSON integer 1-12.
• Returns 28, 29, 30, or 31 depending on the month and whether year is a leap year (February is 29 in leap years, 28 otherwise).

Input

• year (integer, required): min 1; max 9999
• month (integer, required): min 1; max 12

Output

• days (integer, required): min 28; max 31

Limits

• year min: 1
• year max: 9999

Example

Request input:

{
  "year": 2024,
  "month": 2
}

Response:

{
  "result": {
    "days": 29
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "iso-date-days-in-month",
  "version": "1.0.0",
  "input": {
    "year": 2024,
    "month": 2
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/iso-date-days-in-month/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"year":2024,"month":2}'

The machine-readable contract is at /v1/tools/iso-date-days-in-month/versions/1.0.0.

CLI

node cli.mjs run iso-date-days-in-month 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• ISO date age: Compute the calendar-aware elapsed years, months, and days between a birth date and an as-of date.
• ISO date add years: Add a signed whole-year delta to a YYYY-MM-DD date, clamping the day if 29 February has no match.
• ISO date last weekday of month: Return the date of the last occurrence of an ISO weekday within a calendar month.
• ISO date month end: Return the last valid calendar day of the year-month of a YYYY-MM-DD date.
• ISO date month start: Return the first calendar day of the year-month of a YYYY-MM-DD date.
• ISO date nth weekday of month: Return the date of the nth occurrence of an ISO weekday within a calendar month.