isValidUtcTimestamp

Unreleased

Not in @northguild/gmt 1.18.0 on npm yet. It is on main and ships in the next release.

Signature

isValidUtcTimestamp(value: string): boolean

Return true when value is a real UTC instant written as YYYY-MM-DDTHH:MM:SS[.f]Z and nothing else: a narrower check than isValidUtc.

• The shape is one spelling of the RFC 3339 §5.6 date-time: a four-digit year, 0000 to 9999 (date-fullyear = 4DIGIT), an upper-case T, a time with seconds, an optional fraction of one to nine digits after a dot (time-secfrac = "." 1*DIGIT; GMT stops at nine because Temporal keeps nanoseconds), and an upper-case Z with nothing after it.
• Use it for a string headed for storage, or for a reader that is not Temporal: the shape is plain RFC 3339, and the one Temporal.Instant.prototype.toString(), called with no options, writes for years 0000 to 9999.
• Use isValidUtc when Temporal is the only reader. It also accepts a time without seconds, a comma before the fraction, an expanded ±YYYYYY year and RFC 9557 annotations; all four are false here.
• A subset of isValidUtc: every string that is true here is true there. The instant is checked as well as the shape, so a day that does not exist is false.
• False for the other spellings §5.6 allows: a lower-case t or z, a space for T (its NOTE), and a numeric offset, +00:00 included. isValidRfc3339DateTime checks the whole grammar, with the same two GMT limits.
• False for a leap second (:60), although §5.6 time-second admits it: GMT rejects leap seconds because Temporal would read one as :59.
• Not one canonical spelling: 12:00:00Z and 12:00:00.000Z are one instant and both are true. A reader may still refuse or round a string that is true here: PostgreSQL has no year 0000 and keeps microseconds. See toPgMicroseconds and precision/.
• False for a non-string.

Parameters

Parameter	Type	Description
value	string	candidate UTC timestamp string

Returns

true when value is a real UTC instant in this shape, or false on invalid input

Examples

import { isValidUtcTimestamp } from "@northguild/gmt/utc/validate";

isValidUtcTimestamp("2026-10-06T12:00:00Z") // true

value

output

 

Source

utc/validate/isValidUtcTimestamp.ts