# ISO 8601 Duration Builder

Convert between natural-language durations and ISO 8601 durations (PnYnMnDTnHnMnS) in both directions with validation of edge cases

> Canonical page: https://elysiatools.com/en/tools/iso-8601-duration-builder

- **Category:** Development

- **Keywords:** iso 8601, duration, interval, pny, time format, converter, natural language, java duration, javascript duration, timedelta

## Overview

Bidirectional converter for ISO 8601 durations. Natural language (e.g. "3 years 2 months 14 days", "2h30m", "3天2小时") parses to canonical P3Y2M14D; ISO strings parse back to readable form with per-component breakdown. Validates the tricky ISO 8601 rules (T-section units, weeks not combined with Y/M/D, decimal only on smallest unit, at least one component).

## Inputs

- **Input** (text): Natural: 3 years 2 months 14 days · 2h30m · 3天2小时 ISO 8601: P3Y2M14D · PT2H30M · P1WT12H
- **Direction** (select)

## When to use

- When writing configuration files, API payloads, or database schemas that require strict ISO 8601 duration formats.
- When parsing and debugging complex ISO 8601 duration strings received from external APIs or system logs.
- When converting user-friendly, natural-language time intervals into standardized machine-readable formats.

## How it works

- Enter a natural-language duration or an ISO 8601 duration string into the input field.
- Select the conversion direction, or leave it on Auto to let the tool detect the input format.
- Review the generated output, which displays the converted format alongside a detailed component breakdown.

## Use cases

- Generating standardized duration strings for system configuration files or environment variables.
- Translating machine-generated ISO 8601 intervals into human-readable text for application dashboards.
- Validating that duration strings comply with strict ISO 8601 standards before saving them to a database.

## Frequently asked questions

### What is the basic format of an ISO 8601 duration?

It follows the pattern PnYnMnDTnHnMnS, where P is the duration designator, Y/M/D represent date units, T is the time designator, and H/M/S represent time units.

### Can I mix weeks with other units in ISO 8601?

No, standard ISO 8601 rules state that weeks (W) should not be combined with other date or time units like years, months, or days.

### Where can decimal fractions be used in a duration string?

Decimals are only permitted on the smallest, final unit present in the duration string, such as PT1.5H or PT1H30.5M.

### What does the 'T' designator signify in the duration string?

The 'T' designator separates date units (Years, Months, Days) from time units (Hours, Minutes, Seconds) to prevent ambiguity between Months (M) and Minutes (M).

### Does this tool support negative durations?

The tool validates standard ISO 8601 duration components and outputs canonical positive intervals based on the input provided.

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