feat(dates): allow configurable default timezone

docs/configuration.md

@@ -35,6 +35,7 @@ This part of the configuration concerns anything that can affect the whole site.
   - `{ provider: 'cabin' }` or `{ provider: 'cabin', host: 'https://cabin.example.com' }` (custom domain): use [Cabin](https://withcabin.com);
   - `{provider: 'clarity', projectId: '<your-clarity-id-code' }`: use [Microsoft clarity](https://clarity.microsoft.com/). The project id can be found on top of the overview page.
 - `locale`: used for [[i18n]] and date formatting
+- `timezone`: timezone for interpreting dates (IANA format), when not specified in the datetime string; defaults to the system's local zone.
 - `baseUrl`: this is used for sitemaps and RSS feeds that require an absolute URL to know where the canonical 'home' of your site lives. This is normally the deployed URL of your site (e.g. `quartz.jzhao.xyz` for this site). Do not include the protocol (i.e. `https://`) or any leading or trailing slashes.
   - This should also include the subpath if you are [[hosting]] on GitHub pages without a custom domain. For example, if my repository is `jackyzha0/quartz`, GitHub pages would deploy to `https://jackyzha0.github.io/quartz` and the `baseUrl` would be `jackyzha0.github.io/quartz`.
   - Note that Quartz 4 will avoid using this as much as possible and use relative URLs whenever it can to make sure your site works no matter _where_ you end up actually deploying it.

quartz/build.ts

@@ -56,6 +56,7 @@ async function buildQuartz(argv: Argv, mut: Mutex, clientRefresh: () => void) {
 
   LuxonSettings.throwOnInvalid = true
   LuxonSettings.defaultLocale = cfg.configuration.locale
+  if (cfg.configuration.timezone) LuxonSettings.defaultZone = cfg.configuration.timezone
 
   const pluginCount = Object.values(cfg.plugins).flat().length
   const pluginNames = (key: "transformers" | "filters" | "emitters") =>

quartz/cfg.ts

@@ -75,6 +75,12 @@ export interface GlobalConfiguration {
    * Region Codes: https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2
    */
   locale: ValidLocale
+  /**
+   * The default timezone when handling dates.
+   * Valid options are "system" (default), "utc", an IANA string, or a UTC offset
+   * https://moment.github.io/luxon/#/zones?id=specifying-a-zone
+   */
+  timezone?: "system" | string
 }
 
 export interface QuartzConfig {