ISO date-time diff seconds

iso-datetime-diff-seconds · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

Return the signed whole-second difference between two strict UTC ISO-8601 datetimes.

Use when you need to: iso datetime diff seconds · difference between utc datetimes in seconds · utc datetime difference in seconds.

Supported

• iso datetime diff seconds
• difference between utc datetimes in seconds
• utc datetime difference in seconds

Not supported

• leap seconds
• time zones
• offsets other than Z
• fractional seconds
• locale
• ISO-8601 duration strings
• calendar month or year difference
• DST

Behavior

• start and end must each match YYYY-MM-DDTHH:MM:SSZ with zero-padded fields and a real proleptic Gregorian UTC civil time.
• Years are 0001-9999. Days are linear 86400-second POSIX days. There are no leap seconds, fractional seconds, space separators, or offsets other than Z.
• The result is the canonical integer string of end minus start in whole seconds on the UTC timeline.
• The difference is negative when end is earlier than start, and 0 when the instants are equal.

Input

• start (string, required): min length 20; max length 20; pattern ^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$
• end (string, required): min length 20; max length 20; pattern ^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$

Output

• seconds (string, required): pattern ^(0|-?[1-9][0-9]*)$

Limits

• min year: 1
• max year: 9999

Example

Request input:

{
  "start": "2026-09-11T12:00:00Z",
  "end": "2026-09-11T12:01:30Z"
}

Response:

{
  "result": {
    "seconds": "90"
  }
}

How to call it

MCP

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

{
  "id": "iso-datetime-diff-seconds",
  "version": "1.0.0",
  "input": {
    "start": "2026-09-11T12:00:00Z",
    "end": "2026-09-11T12:01:30Z"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/iso-datetime-diff-seconds/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"start":"2026-09-11T12:00:00Z","end":"2026-09-11T12:01:30Z"}'

The machine-readable contract is at /v1/tools/iso-datetime-diff-seconds/versions/1.0.0.

CLI

node cli.mjs run iso-datetime-diff-seconds 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• ISO date-time add seconds: Add a signed whole-second delta to a strict UTC ISO-8601 datetime.
• 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).
• 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.