vcp: normalize timezone offset

[gRegorLove]

In https://microformats.org/wiki/value-class-pattern#Date_and_time_parsing

Reference:

• XX is the time zone hours offset, from 00 to 12 with optional leading 0 for values less than 10.
• YY is the time zone minutes offset, from 00 to 59, though in practice only 00, 15, 30, 45 minute offsets are used in global timezones.

Change the later line:

• However the colons ":" separating the hours and minutes of any timezone offset are optional and discouraged in order to make it less likely that a timezone offset will be confused for a time.

To:

• However the colons ":" separating the hours and minutes of any timezone offset are optional. If the offset uses XX:YY format, remove the colon so it is XXYY format. This makes it less likely that a timezone offset will be confused for a time.

The final two bullets in this section seem to imply this behavior by the two timezone examples not including colons. This suggested spec change will make it explicit and also let us resolve microformats/tests#29.

• YYYY-MM-DD HH:MM-XXYY or YYYY-MM-DD HH:MM:SS-XXYY or
• YYYY-MM-DD HH:MM+XXYY or YYYY-MM-DD HH:MM:SS+XXYY - both time and timezone offset were specified.

[gRegorLove]

Relevant from this comment #27 (comment)

The list of possible VCP assembled output syntaxes was intended to be comprehensive.

[gRegorLove]

Testing current parsers:

<div class="h-event">
    <h1 class="p-name">Happy 17th birthday microformats.org</h1>
    <p class="dt-start">
        <time class="value" datetime="2022-06-20">20 June</time>, from
        <time class="value">00:00-08:00</time> 
    </p>
</div>

Normalizes timezone offset as described above:

• ✔️ Go
• ✔️ php-mf2
• ❌ mf2py
• ✔️ Ruby
• ❌ Haskell
• ✔️ JS
• ❌ Rust
• could not test node, https://node.microformats.io is down currently

[sknebel]

sounds reasonable to me (+1 with hat as mf2py contributor)

[aimee-gm]

The working JS parser: https://github.com/microformats/microformats-parser

[jalcine]

Throwing in the Rust parser into the mix at https://rust.microformats.io, it defaults to adding colons in offsets if they were provided initially.

(Originally published at: https://jacky.wtf/2022/6/S0Jx)

[jalcine]

(+1) I'm in favor of the change of normalizing the timezone offset such that the colon is not present. The Rust implementation is currently capable of checking if it was there when it was authored. If it's either always or not present, there's a bit of logic I can remove (less code is good).

(Originally published at: https://jacky.wtf/2022/6/Kwm5)

[gRegorLove]

Resolution: proposal accepted.

No objections in above discussion, 4 parsers already implement it, and positive opinions (+1) from a few implementers on the proposal.

Updated spec with this revision: https://microformats.org/wiki/index.php?title=value-class-pattern&oldid=70522