ISO 8601 is an international standard developed by the International Organization for Standardization (ISO) that provides a clear and unambiguous way to represent dates and times. It was created to remove the confusion caused by the many different date and time formats used worldwide, which can lead to misinterpretation and costly errors, especially in global operations such as scheduling meetings, deliveries, contracts, or travel.
The core principle of ISO 8601 is to present date and time values in a fixed order from the largest to the smallest unit: year, month (or week), day, hour, minute, second, and fraction of second. This sequence allows chronological sorting by simple text comparison.
The standard defines two main notation styles:
Extended format: Uses separators for readability, such as hyphens between date fields and colons between time values. For example, September 6, 2022, is written as "2022-09-06".
Basic format: Omits separators for compactness, such as "20220906". However, ISO advises avoiding this format in plain text to prevent ambiguity.
Key format features include:
Date expressed as YYYY-MM-DD (year-month-day).
Time represented based on a 24-hour clock as hh:mm:ss and fractions.
Use of "T" to separate date and time elements, e.g., "2022-09-06T18:00:00".
Support for Coordinated Universal Time (UTC) with a "Z" suffix, e.g., "2022-09-06T18:00:00Z".
Ability to express local time with UTC offsets, e.g., "2022-09-06T18:00:00+02:00".
Representation of time intervals and recurring times.
Optional reduction of precision by dropping less significant elements, for example, "2022-09" to indicate just the month and year.
ISO 8601 helps people and computer systems worldwide to interpret date and time data consistently, reducing errors and improving interoperability across cultures and technologies.