ISO date-time truncate

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

Truncate a strict UTC ISO-8601 datetime toward UTC zero at day, hour, minute, or second.

Use when you need to: iso datetime truncate · truncate utc datetime · floor iso datetime to unit.

Supported

• iso datetime truncate
• truncate utc datetime
• floor iso datetime to unit

Not supported

• round or ceil
• truncate to week, month, or year
• leap seconds
• time zones
• offsets other than Z
• fractional seconds
• locale
• DST

Behavior

• datetime must 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.
• unit must be exactly day, hour, minute, or second.
• Truncation zeros smaller fields toward UTC zero: day to T00:00:00Z, hour to HH:00:00Z, minute to HH:MM:00Z, second is identity.
• The result is formatted YYYY-MM-DDTHH:MM:SSZ and stays on the same calendar date as the input.

Input

• datetime (string, required): min length 20; max length 20; pattern ^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$
• unit (one of "day", "hour", "minute", "second", required)

Output

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

Limits

• min year: 1
• max year: 9999
• units: ["day","hour","minute","second"]

Example

Request input:

{
  "datetime": "2026-09-11T12:34:56Z",
  "unit": "hour"
}

Response:

{
  "result": {
    "datetime": "2026-09-11T12:00:00Z"
  }
}

How to call it

MCP

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

{
  "id": "iso-datetime-truncate",
  "version": "1.0.0",
  "input": {
    "datetime": "2026-09-11T12:34:56Z",
    "unit": "hour"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/iso-datetime-truncate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"datetime":"2026-09-11T12:34:56Z","unit":"hour"}'

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

CLI

node cli.mjs run iso-datetime-truncate 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 clamp: Clamp a strict UTC ISO-8601 datetime into an inclusive [min, max] range.
• ISO date-time compare: Compare two strict UTC ISO-8601 datetimes and return -1, 0, or 1.
• ISO date-time diff seconds: Return the signed whole-second difference between two strict UTC ISO-8601 datetimes.
• ISO date add: Add a signed whole-day delta to a strict YYYY-MM-DD calendar date.
• ISO date add months: Add a signed month count to a YYYY-MM-DD date, clamping the day to the target month.