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mnot opened this issue Oct 12, 2020 · 4 comments · Fixed by #484
Closed

UTC in dates #472

mnot opened this issue Oct 12, 2020 · 4 comments · Fixed by #484

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@mnot
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mnot commented Oct 12, 2020

Caching 4.2 says:

A cache recipient should consider a date with a zone abbreviation other than GMT or UTC to be invalid for calculating expiration.

But Semantics 5.7.7 says nothing about using UTC in dates.

Is this intentional? Similar question regarding the mismatch in case sensitivity.

@mnot mnot self-assigned this Oct 18, 2020
@mnot
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mnot commented Oct 20, 2020

Based on this test, it appears that some implementations do support UTC, but only about half of those tested, so this isn't interoperable.

So, we can't mandate supporting UTC, but neither can we make it non-conformant to support it as a recipient.

My inclination at this point is to slightly change this to clarify it, something like:

A cache recipient SHOULD consider a date with a zone abbreviation other than GMT to be invalid for calculating expiration, but it MAY also accept UTC for historic reasons.

(also, editorially I can't help but wonder if GMT and UTC should be in quotes in that text)

@mnot
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mnot commented Oct 20, 2020

This language also appears to have been introduced in 7234; the closest relevant language in 2616 is:

      - If an HTTP header incorrectly carries a date value with a time
        zone other than GMT, it MUST be converted into GMT using the
        most conservative possible conversion.

@reschke
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reschke commented Oct 20, 2020

The mention of UTC was added in https://trac.ietf.org/trac/httpbis/changeset/2397. Backout?

@mnot
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mnot commented Oct 21, 2020

I'm OK to back it out; @royfielding?

mnot added a commit that referenced this issue Oct 22, 2020
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