📅 Fix date representation (again)

[agoose77]

Presently, our datetime handling is not quite right. We sometimes (due to Date) parse dates in the local timezone, but we render them in templates as UTC.

i.e. for BST=UTC+1

> // A valid UTC date
> new Date(Date.UTC(2024, 6, 1))
2024-07-01T00:00:00.000Z
> // The same date without UTC
> new Date(2024, 6, 1)
2024-06-30T23:00:00.000Z

where the Z suffix indicates UTC. At the moment, we then ask for getUTCDate(), which returns 30 because the code parses the date as the 00:00:00 timestamp in BST, which is 23:00:00 the previous day in UTC.

Instead, we should assume that a user is entering a valid "local"/"wall time" date. This PR fixes mystmd's validation to explicitly ignore timezones and directly take the day/month information from the Date object.

Should fix #1357

See also https://tc39.es/proposal-temporal/docs/ambiguity.html

[changeset-bot]

🦋 Changeset detected

Latest commit: 034a329

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
simple-validators	Patch
myst-templates	Patch

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[agoose77]

Escape YAML interpretation

[agoose77]

Ugh, yikes, more problems:

When the time zone offset is absent, date-only forms are interpreted as a UTC time and date-time forms are interpreted as local time. This is due to a historical spec error that was not consistent with ISO 8601 but could not be changed due to web compatibility. See Broken Parser – A Web Reality Issue.

i.e.

> process.env.TZ = "America/Anchorage"
'America/Anchorage'
> new Date("2024-06-06")
2024-06-06T00:00:00.000Z
> new Date("2024-06-06 19:00")
2024-06-07T03:00:00.000Z

We really need a better way to handle this. I'll update the main body of the PR dsecription.

[agoose77]

I think we can use moment.js's parseZone function. This assumes ambiguous input is UTC, and non-ambiguous input keeps the timezone. In other words, there's no timezone shift happening, which means we can use the raw-parsed components.

[agoose77]

The history of this PR will be confusing. I'll open a new one!