ISO Date Formatter

1. Use the "Format Date to ISO" tab to pick a date and see it in all ISO 8601 variations.
2. Use the "Parse ISO to Readable" tab to paste an ISO date string and see its human-readable components.
3. Click "Copy" on any result card to copy the value to your clipboard.
4. Try the examples to see how different ISO formats are parsed.

What is ISO 8601?

ISO 8601 is the international standard for representing dates and times in a clear, unambiguous format. First published in 1988, it defines a consistent way to express calendar dates, times, time intervals, and durations. The most common form is YYYY-MM-DDTHH:mm:ss.sssZ, such as 2024-03-15T14:30:00.000Z. The key advantage is that it removes ambiguity: while "01/02/03" could mean January 2 or February 1 depending on locale, 2003-01-02 always means January 2, 2003.

ISO 8601 Format Variations

The standard supports several date representations. Calendar dates use YYYY-MM-DD (e.g., 2024-03-15). Week dates use YYYY-Www-D (e.g., 2024-W11-5 for Friday of week 11). Ordinal dates use YYYY-DDD (e.g., 2024-075 for the 75th day of the year). Times can be appended with a T separator: 2024-03-15T14:30:00. Timezone information is expressed as Z for UTC or an offset like +05:30 or -08:00. Each variation serves different use cases, from API responses to log file timestamps.

Common Use Cases

• Formatting dates for REST API requests and responses
• Storing dates in databases with timezone information
• Parsing log file timestamps from different systems
• Generating ISO date strings for data interchange between services
• Converting between human-readable dates and machine-parseable formats

Why Developers Should Use ISO 8601

ISO 8601 dates sort correctly as plain text (lexicographic ordering matches chronological ordering), which simplifies database queries and file sorting. They are natively understood by every major programming language: JavaScript's Date constructor, Python's datetime.fromisoformat(), Java's Instant.parse(), and Go's time.Parse(time.RFC3339) all handle ISO 8601. The format also includes timezone information, preventing the class of bugs that arises when dates are stored without timezone context and later interpreted in different timezones.

For Unix timestamp conversions, use the Unix Timestamp Converter. To convert between timezones, try the Timezone Converter. For calculating differences between dates, see the Date Difference Calculator.