Date: Ensure timezone offset is a number

[ryelle]

When using a UTC offset timezone (instead of a named timezone), the offset is saved as a numeric string. This is not understood by moment, which expects either a number or a formatted string (ex "+08:00"). This means dates are not formatted correctly for sites with UTC timezones. You can see this by changing the settings on a site between 2 options that represent the same time, ex "UTC-7" and "Vancouver".

wp.date.dateI18n('F j, Y g:i a', 1601532000000 )
  -> Vancouver: "September 30, 2020 11:00 pm"
  -> UTC-7: "October 1, 2020 2:00 am" (this is my local time, EDT)

Alternately you can see the problem more clearly by trying to pass in a string timezone offset to date:

wp.date.date('F j, Y g:i a', 1601532000000, '-7' )
  ⚠️ Moment Timezone has no data for -7.

Fixes #21977

How has this been tested?

Tested in browser as described above (with UTC-7 and UTC+1:30), and ran unit tests.

Types of changes

Bug fix (non-breaking change which fixes an issue)

[github-actions]

Size Change: +4 B (0%)

Total Size: 1.17 MB

Filename	Size	Change
build/date/index.js	31.9 kB	+4 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
build/a11y/index.js	1.14 kB	0 B
build/annotations/index.js	3.52 kB	0 B
build/api-fetch/index.js	3.35 kB	0 B
build/autop/index.js	2.72 kB	0 B
build/blob/index.js	620 B	0 B
build/block-directory/index.js	8.61 kB	0 B
build/block-directory/style-rtl.css	943 B	0 B
build/block-directory/style.css	942 B	0 B
build/block-editor/index.js	129 kB	0 B
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build/block-library/editor.css	8.6 kB	0 B
build/block-library/index.js	135 kB	0 B
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build/deprecated/index.js	772 B	0 B
build/dom-ready/index.js	568 B	0 B
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build/format-library/style-rtl.css	547 B	0 B
build/format-library/style.css	548 B	0 B
build/hooks/index.js	1.74 kB	0 B
build/html-entities/index.js	621 B	0 B
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build/is-shallow-equal/index.js	709 B	0 B
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build/rich-text/index.js	13.5 kB	0 B
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build/warning/index.js	1.13 kB	0 B
build/wordcount/index.js	1.17 kB	0 B

_{compressed-size-action}

[vcanales]

I realize this is a bit stale, but LGTM!

I've got to note though that __experimentalGetOffset does not exist—#21977 (comment) is probably referencing __experimentalGetSettings. This change still affects formatting when using other functions within @wordpress/date.

[jeremyfelt]

I've got to note though that __experimentalGetOffset does not exist—#21977 (comment) is probably referencing __experimentalGetSettings. This change still affects formatting when using other functions within @wordpress/date

Thanks for this! I'm not sure where I got __experimentalGetOffset() from. I've updated the title and description in #21977 to better reflect the naming. :)

[ciampo]

Pinging @noisysocks in the context of #21977 (comment)

[t-hamano]

I have checked the latest trunk status.
Perhaps a similar change is included in #39670.

gutenberg/packages/date/src/index.js

Line 614 in 1b5994a

return dateMoment.utcOffset( +settings.timezone.offset );

@noisysocks
Can we close this PR?

[noisysocks]

Yes #39670 included essentially what's in this PR.