Date

Purpose

All date values transmitted across any interface MUST follow the ISO-8601 format. This ensures deterministic interpretation across all systems, languages, and timezones.

Conceptual Model

A date represents a calendar day without time-of-day or timezone information. The canonical representation is the ISO-8601 extended format: YYYY-MM-DD.

Rules

• All date fields MUST use the YYYY-MM-DD format
• Unix Epoch representations MUST be rejected
• Local timezone offsets MUST NOT be included in date-only fields
• Non-ISO separators (slash, space) MUST be rejected

Examples

Valid

{ "created_at": "2026-02-16" }

Invalid

{ "created_at": "16-02-2026" }

{ "created_at": "16/02/2026" }

{ "created_at": "02-16-2026" }

Validation Rules

Regex: ^\d{4}-\d{2}-\d{2}$

Validation MUST occur at contract boundary (API gateway, event schema registry, message broker).

Enforcement Rules

• Constraint: Reject any payload using Unix Epoch or local timezone offsets.
• Reference: ISO 8601

References

• ISO-8601 - Date and time format standard

Rationale

ISO-8601 YYYY-MM-DD is unambiguous across locales (unlike DD/MM/YYYY vs MM/DD/YYYY), sorts lexicographically, and is natively supported by all major programming languages and databases.

Version History

Version	Date	Change
1.0.0	2026-02-16	Initial definition