Existing Wording: instant: ...The time SHALL be known at least to the second and SHALL include a time zone. Note: This is intended for precisely observed times (typically system logs etc.), and not human-reported times - for them, use date and dateTime.

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Regex: ([0-9]([0-9]([0-9][1-9]|[1-9]0)|[1-9]00)|[1-9]000)(0[1-9]|1[0-2])(0[1-9]|[1-2][0-9]|3[0-1])T([01][0-9]|2[0-3]):[0-5][0-9][0-5][0-9]|60)(\.[0-9]+)?(Z|(+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))

Comment:

"be known": to who? Replace with "given", "indicated", or "accurate".

"for them" - replace with "for those"

The regex allows arbitrary precision subseconds. Should it only allow (or require) up to 3?

I can follow most of the regex, except for the part on year. What is it supposed to be confirming? What is wrong with "[0-9]

"? Confirm that such a complex expression is required.

The regex comment also applies to date and dateTime.

Summary:

Clarify instant datatype