RFC3339 is better than ISO8601 since it doesn’t allow some of the esoteric formats, and allows some useful formats that ISO8601 doesn’t (like separating date and time by a space instead of by T)
For example, 2026-W32-1 is also a valid ISO8601 date: Monday on the 32nd week of 2026. That format isn’t allowed with RFC3339.
RFC3339 is better than ISO8601 since it doesn’t allow some of the esoteric formats, and allows some useful formats that ISO8601 doesn’t (like separating date and time by a space instead of by
T)For example,
2026-W32-1is also a valid ISO8601 date: Monday on the 32nd week of 2026. That format isn’t allowed with RFC3339.https://ijmacd.github.io/rfc3339-iso8601/