DateTime — GraphQL Custom Scalar

Author – andimarek

Date - 2022-10-18

This is a String-based Scalar.


This Scalar represents an exact point in time. This point in time is specified by having an offset to UTC and does not use a time zone.

It is a slightly refined version of RFC 3339 including the errata.

All definitions of RFC 3339 are adopted and nothing is added or removed unless explicitly mentioned here.

The following refinements/clarifications apply:

Only “date-time”

This scalar represents a “date-time” as specified in section 5.6 of RFC 3339.

The other productions in section 5.6 are only used to support “date-time” but never stand alone for this Scalar.

Non-optional exact milliseconds

RFC 3339 defines time-secfrac optional as:

time-secfrac    = "." 1*DIGIT (Meaning 1 or more DIGIT)

This allows for an unlimited numbers of digits. For this scalar the rule is not optional anymore and refined as:

time-secfrac    = "." DIGIT DIGIT DIGIT

consisting always of exact three digits representing milliseconds.

No ‘Unknown Local Offset Convention’

Section 4.3 says:

If the time in UTC is known, but the offset to local time is unknown,
this can be represented with an offset of "-00:00".

In order to simplify this Scalar this convention is dropped and an offset of -00:00 is not allowed.


The general format is described in RFC3339 Section 5.6.

Under consideration of the additional restrictions and explanations above here are valid and invalid examples:

These are valid examples:

String Explanation
2011-08-30T13:22:53.108Z A DateTime with UTC offset (+00:00).
2011-08-30T13:22:53.108+00:00 A DateTime with +00:00 which is the same as UTC.
2011-08-30t13:22:53.108z The z and t may be lower case.
2011-08-30T13:22:53.108-03:00 A DateTime with -3h offset.
2011-08-30T13:22:53.108+03:30 A DateTime with +3h 30min offset.

These are invalid examples:

String Why is it invalid
2011-08-30T13:22:53.108-03 The minutes of the offset are missing.
2011-08-30T13:22:53.108912Z Too many digits for fractions of a second. Exactly three expected.
2011-08-30T24:22:53Z Fractions of a second are missing.
2011-08-30T13:22:53.108 No offset provided.
2011-08-30 No time provided.
2011-08-30T13:22:53.108-00:00 Negative offset (-00:00) is not allowed
2011-08-30T13:22:53.108+03:30:15 Seconds are not allowed for the offset
2011-08-30T24:22:53.108Z 24 is not allowed as hour of the time.
2010-02-30T21:22:53.108Z 30th of February is not a valid date
2010-02-11T21:22:53.108Z+25:11 25 is not a valid hour for offset


The recommended name is DateTime. An alternative is OffsetDateTime.

Date is potentially misleading as this Scalar also specifies a time, not only a date.


The result must be formatted as described above with the further requirement that UTC offset should be always be represented as Z and not +00:00 and the two divider characters T and Z are always uppercase, never t or z.


As Input every valid String as described above must be accepted.

  1. 1Overview
  2. 2Name
  3. 3Result
  4. 4Input