replace jiff by chrono. add support for localization of date and time

[daxcore]

Summary

Hey. This pull request replaces the jiff crate with chrono, chrono-tz, and localzone for handling time formatting, time zones, and locale customization in the clock widget. It introduces support for user-specified locales, improving i18n by allowing time display in different languages and regional formats.

Motivation

• The jiff crate is still limited for localized time formatting.
• chrono offers a stable API with broad support for date/time formatting using strftime.
• chrono-tz supports IANA time zones directly.
• The localzone crate enables automatic detection of the system's time zone.
• Added locale customization so the clock widget can adapt to the user’s preferred language/region.

This improves internationalization and configurability of the clock component.

Changes

Dependencies

• Added chrono with unstable-locales feature for localized formatting.
• Added chrono-tz for IANA timezone parsing.
• Added localzone for detecting the system’s local timezone.
• Removed jiff.

Configuration (regreet.sample.toml)

• Updated the documentation link to chrono’s strftime reference.
• Added new locale option, allowing users to specify the locale for formatting:

        [widget.clock]
        format = "%a %H:%M"
        timezone = "America/Chicago"
        label_width = 150
        locale = "en_US"

• This controls language-specific elements (e.g., month, weekday, AM/PM).

Code (widget/clock.rs)

• Replaced jiff::TimeZone and formatting logic with chrono::Utc, chrono_tz::Tz, and localized formatting (format_localized).
• Implemented timezone parsing:
  • User-specified timezone (Tz) is preferred.
  • Falls back to system local timezone via localzone.
  • Defaults to UTC if none found.
• Implemented deserializer for Locale, with validation and fallback behavior.
• Updated ClockConfig to include locale field.
• Updated Clock implementation:
  • Current time is updated using Utc::now().with_timezone(...).
  • Formatted using the configured Locale.

Benefits

• Improved configurability through locales.
• Consistent formatting with chrono’s ecosystem.
• Reliable timezone handling with system fallback via localzone.
• Enhanced internationalization support for multilingual deployments.

[BurntSushi]

The jiff crate is still limited for localized time formatting.

You can use jiff-icu to tie into the icu crate for modern Unicode localized datetime formatting.

Jiff does everything else in your list.

[rharish101]

Thanks for the PR. I rebased it and added fallbacks to system tz/locale if they aren't specified in the config. @daxcore Could you review and test the new changes?

You can use jiff-icu to tie into the icu crate for modern Unicode localized datetime formatting.

Unfortunately, I can't find any easy way to format in icu with a dynamic format string. If the format is fixed, it's pretty straightforward (as jiff-icu shows in its docs), but that's not the case here, as the format is specified by users in the config.

[daxcore]

@rharish101 works pretty well for me. thx. built and tested successfully. 👍