Define timestamp format carefully

[aphillips]

DID Document Metadata
https://www.w3.org/TR/did-resolution/#dfn-created

DID document metadata SHOULD include a created property to indicate the timestamp of the Create operation. The value of the property MUST be a string formatted as an XML Datetime normalized to UTC 00:00:00 and without sub-second decimal precision. For example: 2020-12-20T19:17:47Z.

The definition of created (shown here) defines the intended timestamp format. Several other metadata values (updated, nextUpdate) also use this sort of time stamp.

It would probably be a good idea to separately define the value and to improve the description for clarity. In particular, the operation "normalized to UTC 00:00:00" is undefined.

(Note: I do not have a quibble with the design. This is the right design.)

[wip-abramson]

@aphillips we discussed this on the call today. Does the Internationalization group have a recommended reference we could cite for this?

This has been defined in the VCDM - https://w3c.github.io/vc-data-model/#representing-time - which we could reference. But ideally, we would avoid introducing a normative dependency on the VCDM.

Also, we do not want to replicate this spec text in our spec.

Thanks

[w3cbot]

This was discussed during the #did meeting on 25 September 2025.

View the transcript

Define timestamp format carefully #203

<ottomorac> w3c/did-resolution#203

ottomorac: this is about the timestamp format, etc...
… something about normalizing to UTC

WIp: I don't have many opinions on many of these i18n issues
… but we just need to address them for horiz review
… like, how do we even define the operation of normalizing to UTC?

<manu> https://w3c.github.io/vc-data-model/#representing-time

manu: we do have responses, like the one from VC DM, we should just point to that
… definitely not copy paste (it's too much text), but rerference

Wip: so we can just say 'as defined by VC DM'?

manu: danger here is pulling in a normative dependency on VC DM, which we don't want to do
… but there aren't normative statements in that section. so it wouldn't be a straight up dependency
… yeah, we should just point to this section

ottomorac: any volunteers?

WIp: I don't know if I want to do a PR, but I could write a comment -- do we have a section that you can reference, see what they say
… this seems like it has been solved by other specs

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[aphillips]

I don't have a ready Normative reference. I believe VCDM created that text because there is not, AFAIK, a specific reference that does UTC normalization with no fractional seconds elsewhere. It's a permitted format in e.g. XMLSchema Datetime and it is the Right Thing To Do. It's just not formally defined.

As you note, taking a dependency on VCDM is not ideal. We should help you and other groups (including the VC folks) by making a reference in a foundational spec. In particular, I'd suggest adding this to Infra.