fix: date-only column display shifted one day behind in non-UTC timezones

[tareko]

Bug

The discovery of this bug and code to fix it were assisted by AI: GLM 5.2

Date-only columns display the date one day behind the entered value for users in timezones behind UTC (e.g. America/Toronto UTC-4).

Steps to reproduce:

1. Create a date-only column (not datetime, just date)
2. Enter a date (e.g. 2025-08-25)
3. The table view shows the previous day (e.g. Aug 24, 2025)
4. Clicking to edit shows the correct date — the bug is only in the display

Root cause

In datetimeDate.js, formatValue parsed date-only values (e.g. "2025-08-25") using the datetime format 'YYYY-MM-DD HH:mm:ss':

formatValue(value) {
    return Moment(value, 'YYYY-MM-DD HH:mm:ss').format('ll')
}

Since the input string doesn't match the format (no time component), Moment.js falls back to ISO 8601 parsing, which interprets date-only strings as UTC midnight. When .format('ll') then converts to the user's local timezone, the date shifts back one day for users behind UTC.

Fix

Use 'YYYY-MM-DD' as the Moment parse format — this matches the actual stored value format and ensures local-timezone parsing:

formatValue(value) {
    return Moment(value, 'YYYY-MM-DD').format('ll')
}

This is consistent with getDateFormat() in TableCellDateTime.vue, which already uses 'YYYY-MM-DD' for the edit mode — explaining why editing showed the correct date while the cell display didn't.

Fixes #2705

[Copilot]

Pull request overview

Fixes an off-by-one-day display bug for date-only columns in the Nextcloud Tables frontend when viewed in timezones behind UTC by ensuring date strings are parsed using the correct date-only format.

Changes:

• Update DatetimeDateColumn.formatValue() to parse stored date-only values using YYYY-MM-DD (matching the stored format) before formatting for display.

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