ISO date compare

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

Compare two YYYY-MM-DD calendar dates and return -1, 0, or 1.

Use when you need to: iso date compare · compare two dates · date ordering.

Supported

• iso date compare
• compare two dates
• date ordering

Not supported

• locale collation
• datetime comparison
• timezones

Behavior

• a and b are strict YYYY-MM-DD proleptic Gregorian UTC calendar dates with year 0001-9999.
• Comparison is numeric on the civil day serial, not lexicographic on the string (both agree for zero-padded YYYY-MM-DD, but lexicographic is not the defined rule).
• Returns -1 if a is before b, 0 if equal, 1 if a is after b.

Input

• a (string, required): min length 10; max length 10; pattern ^\d{4}-\d{2}-\d{2}$
• b (string, required): min length 10; max length 10; pattern ^\d{4}-\d{2}-\d{2}$

Output

• comparison (one of -1, 0, 1, required)

Limits

• year min: 1
• year max: 9999

Example

Request input:

{
  "a": "2026-01-01",
  "b": "2026-01-02"
}

Response:

{
  "result": {
    "comparison": -1
  }
}

How to call it

MCP

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

{
  "id": "iso-date-compare",
  "version": "1.0.0",
  "input": {
    "a": "2026-01-01",
    "b": "2026-01-02"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/iso-date-compare/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"a":"2026-01-01","b":"2026-01-02"}'

The machine-readable contract is at /v1/tools/iso-date-compare/versions/1.0.0.

CLI

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

Get the client at /clients/cli/.

Related tools

• ISO date business days count: Count the business days in an inclusive date range, skipping caller-supplied weekend weekdays and holidays.
• ISO date range list: Enumerate the dates in an inclusive [start, end] range stepped by a whole number of days.
• ISO date weekday occurrences in range: List every date within an inclusive date range that falls on a given ISO weekday.
• ISO date-time compare: Compare two strict UTC ISO-8601 datetimes and return -1, 0, or 1.
• ISO date age: Compute the calendar-aware elapsed years, months, and days between a birth date and an as-of date.
• ISO date difference: Whole days from start to end as a canonical integer string (end - start).