What is ISO 8601?
ISO 8601 is an international standard for representing dates and times in a clear, unambiguous format, using the pattern YYYY-MM-DDTHH:MM:SS with optional timezone information.
Quick Facts
| Full Name | ISO 8601 Date and Time Format |
|---|---|
| Created | 1988 (first edition), 2019 (current edition) |
| Specification | Official Specification |
How It Works
ISO 8601 is the globally recognized standard for date and time representation, designed to eliminate ambiguity that arises from different regional date formats. The format places the largest time unit (year) first, followed by month, day, hours, minutes, and seconds. The 'T' character separates date from time. Timezone information can be appended as Z (UTC/Zulu time) or as an offset like +05:30 or -08:00. For example, '2024-03-15T14:30:00Z' represents March 15, 2024 at 2:30 PM UTC. The format supports various precisions—from just the year (2024) to nanoseconds. ISO 8601 is essential for data interchange, APIs, databases, and log files where consistent parsing across different systems and locales is required. Most programming languages have built-in support for parsing and formatting ISO 8601 dates.
Key Characteristics
- Unambiguous format: YYYY-MM-DDTHH:MM:SS
- Largest to smallest units (year → second)
- T separator between date and time
- Z suffix for UTC, or ±HH:MM offset for timezones
- Supports variable precision (year to nanoseconds)
- Lexicographically sortable as strings
Common Use Cases
- API request and response timestamps
- Database datetime storage
- Log files and audit trails
- Calendar and scheduling applications
- Data interchange between different systems
Example
Loading code...Frequently Asked Questions
What does the T mean in ISO 8601 date format?
The 'T' is a delimiter that separates the date portion from the time portion in an ISO 8601 datetime string. For example, in '2024-03-15T14:30:00', the T clearly indicates where the date (2024-03-15) ends and the time (14:30:00) begins.
What does Z mean at the end of an ISO 8601 timestamp?
The 'Z' suffix stands for 'Zulu time' and indicates that the timestamp is in UTC (Coordinated Universal Time). For example, '2024-03-15T14:30:00Z' means March 15, 2024, at 2:30 PM in UTC timezone. Without Z, you can specify timezone offsets like +05:30 or -08:00.
Why is ISO 8601 preferred for APIs and data exchange?
ISO 8601 eliminates date format ambiguity that exists between regions (e.g., MM/DD/YYYY vs DD/MM/YYYY). It's human-readable, machine-parseable, lexicographically sortable as strings, and includes timezone information. Most programming languages have built-in support for parsing and generating ISO 8601 dates.
How do I convert ISO 8601 to a Date object in JavaScript?
JavaScript's Date constructor natively parses ISO 8601 strings. Simply use: new Date('2024-03-15T14:30:00Z'). To convert a Date back to ISO 8601 format, use the toISOString() method: new Date().toISOString() returns a string like '2024-03-15T14:30:00.000Z'.
Does ISO 8601 support time-only or date-only formats?
Yes, ISO 8601 supports multiple precision levels. You can use date-only formats like '2024-03-15' or '2024-03' or even just '2024'. Time-only formats are also valid, such as '14:30:00' or '14:30'. The standard is flexible to accommodate various use cases.