UTC (Coordinated Universal Time)
utc
The primary time standard by which the world regulates clocks and time, serving as the basis for civil timekeeping globally.
ISO 8601
iso-8601
Overview
ISO 8601 is an international standard published by the International Organization for Standardization (ISO) that defines unambiguous representations of dates and times. The most common format is YYYY-MM-DDTHH:mm:ssZ, where T separates the date from the time and Z indicates UTC. This eliminates confusion caused by regional date formats like MM/DD/YYYY vs. DD/MM/YYYY.
Key Formats
The standard covers dates (2026-05-10), times (14:30:00), combined date-times (2026-05-10T14:30:00Z), durations (P1Y2M3D for 1 year, 2 months, 3 days), and intervals (start/end). Time zone offsets are expressed as +HH:mm or -HH:mm, with Z as shorthand for +00:00 (UTC).
Adoption in Software
ISO 8601 is the de facto standard for date-time representation in APIs, databases, and configuration files. JSON does not define a date type, so ISO 8601 strings are the universally accepted convention. JavaScript's Date.toISOString(), Python's datetime.isoformat(), and most database TIMESTAMP types all produce ISO 8601-compliant output.
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