# Duration format clock

`duration-format-clock` · version 1.0.0 · Dates & times (UTC, ISO 8601) · free, no key needed

Format a nonnegative whole or decimal second count as an exact hh:mm:ss[.fraction] clock duration.

**Use when you need to: seconds to hours minutes seconds · format duration as hh:mm:ss · turn decimal seconds into clock time.**

## Decide before calling

Read the [versioned contract](/v1/tools/duration-format-clock/versions/1.0.0) and the supported scope below. Reuse `duration-format-clock@1.0.0` when your input, required output and limits match it. Choose another approach for an unsupported operation.

## Explain the choice

"I can use `duration-format-clock@1.0.0` for seconds to hours minutes seconds. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

## Supported

- seconds to hours minutes seconds
- format duration as hh:mm:ss
- turn decimal seconds into clock time
- display elapsed seconds as a clock
- seconds to time string
- format precise duration

## Not supported

- calendar dates
- negative durations
- rounding fractional seconds

## Behavior

- Accept nonnegative canonical decimal seconds with at most nine fractional digits.
- Hours may exceed 23 and are padded to at least two digits; minutes and seconds are always two digits.
- Preserve the supplied fractional digits exactly; do not round or use binary floating point.

## Input

- `seconds` (string, required): min length 1; max length 20; pattern `^(0|[1-9][0-9]{0,9})(\.[0-9]{1,9})?$`

## Output

- `clock` (string, required): min length 8; max length 22
- `standard_version` (constant "packet-r90-clock-1.0.0", required)

## Limits

- max input bytes: 34

## Example

Request input:

```json
{
  "seconds": "3661.250"
}
```

Response:

```json
{
  "result": {
    "clock": "01:01:01.250",
    "standard_version": "packet-r90-clock-1.0.0"
  }
}
```

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

```json
{
  "id": "duration-format-clock",
  "version": "1.0.0",
  "input": {
    "seconds": "3661.250"
  }
}
```

### HTTP (no key)

```sh
curl -X POST https://computefirst.net/v1/tools/duration-format-clock/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"seconds":"3661.250"}'
```

The machine-readable contract is at [/v1/tools/duration-format-clock/versions/1.0.0](/v1/tools/duration-format-clock/versions/1.0.0).

### CLI

```sh
node cli.mjs run duration-format-clock 1.0.0 --input input.json --base-url https://computefirst.net
```

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [Duration parse clock](/tools/duration-parse-clock): Parse an hh:mm:ss[.fraction] duration and return the exact nonnegative whole or decimal second count.
- [ISO duration structure check](/tools/iso-duration-structure-check): Check a claimed reading of an ISO 8601 duration: well-formedness, components and month/day/time totals.
- [ISO to epoch](/tools/iso-to-epoch): Convert a canonical RFC 3339 UTC timestamp to an exact integer Unix epoch count in the requested unit.
- [Working hours total](/tools/working-hours-total): Total exact elapsed seconds in a versioned working-hours calendar after DST and closure expansion.
- [Duration application check](/tools/duration-application-check): Check a claimed timestamp from adding or subtracting an ISO 8601 duration under explicit offset and month-end rules.
- [Duration convert](/tools/duration-convert): Convert a canonical integer duration between nanosecond-based SI units as an exact rational.