First day of the week preference (Sunday / Monday)

[id0Sch]

Problem

The snooze clock menu includes presets such as Next week: Mon 9:00 AM, which currently assumes Monday as the first day of the week.

The custom snooze calendar now follows the Intl.Locale week start after #12737 and #12745, but there is no settings override. That means the result depends on the OS or browser locale, which is not always the user's preferred week convention.

Proposal

Add a Preferences setting called First day of the week with a Sunday / Monday picker, similar to Linear. The setting should provide an explicit user preference rather than relying only on OS or browser locale.

Scope

• Apply the preference to date pickers.
• Preferably apply it to the Next week snooze preset as well, so that preset is not stuck on Monday.
• A locale-based value could remain the default when no explicit preference has been selected, to preserve current behavior.

Why a setting instead of locale only?

Users may want a different week start from their system or browser locale, and an explicit setting is easier to discover and control. This would also provide a simple Linear-style experience for the existing date picker behavior.

Related

• #12737
• #12745
• #8740
• #8741
• #9011, the unmerged locale-aware Next week proposal
• #11399, configurable snooze times, which is a different request

I plan to open a PR after this Ideas discussion, following the project's CONTRIBUTING guidance.

[gertzgal]

my weekday also starts on Sunday, would love to get this configured, currently, instead of clicking next week, i either:

• go thread by thread, click custom, pick sunday, and type 9:00
• ask an agent in new session to use t3 mcp to snooze threads until 9am sunday, which is somewhat ineffective and slow