fix: luxon plugin

.eleventy.js

@@ -1,7 +1,9 @@
-module.exports = function(eleventyConfig) {
 const { createProxyMiddleware } = require('http-proxy-middleware');
+const { DateTime } = require("luxon");
 const syntaxHighlight = require("@11ty/eleventy-plugin-syntaxhighlight");
 
+module.exports = function(eleventyConfig) {
+
   // Pass through static assets from the "src" directory
   eleventyConfig.addPassthroughCopy("src/css");
   eleventyConfig.addPassthroughCopy("src/js");
@@ -13,25 +15,21 @@ module.exports = function(eleventyConfig) {
 
   eleventyConfig.addPlugin(syntaxHighlight);
 
-  // Add a filter for readable dates using vanilla JS
-  eleventyConfig.addFilter("readableDate", dateObj => {
-    // The toLocaleDateString method can be used to format dates
-    // without any external libraries.
-    // The 'UTC' timeZone option is added to prevent off-by-one day errors.
-    return new Date(dateObj).toLocaleDateString('en-US', {
-      year: 'numeric',
-      month: 'long',
-      day: 'numeric',
-      timeZone: 'UTC' 
-    });
+  // Add a filter for readable dates using Luxon
+  eleventyConfig.addFilter("readableDate", (dateObj) => {
+    if (!dateObj) return "";
+    // When Eleventy parses a date like "2025-08-25", it creates a Date object
+    // at midnight UTC. Using Luxon to format this date while treating it as UTC
+    // prevents the date from shifting to the previous day due to timezone conversion.
+    return DateTime.fromJSDate(dateObj, { zone: 'UTC' }).toFormat('LLLL d, yyyy');
   });
 
   // Add htmlDateString filter for sitemap <lastmod>
-  eleventyConfig.addFilter("htmlDateString", dateObj => {
+  eleventyConfig.addFilter("htmlDateString", (dateObj) => {
     if (!dateObj) return "";
-    // Format date as YYYY-MM-DD for sitemaps
-    const d = new Date(dateObj);
-    return d.toISOString().split("T")[0];
+    // toISODate() will return the date in YYYY-MM-DD format.
+    // We specify UTC zone to ensure the date is not affected by the system's timezone.
+    return DateTime.fromJSDate(dateObj, { zone: 'UTC' }).toISODate();
   });
 
   // Shortcode for creating a callout box

package-lock.json

@@ -13,7 +13,8 @@
         "@11ty/eleventy-plugin-syntaxhighlight": "^5.0.2",
         "cors": "^2.8.5",
         "express": "^4.21.2",
-        "fs-extra": "^11.3.1"
+        "fs-extra": "^11.3.1",
+        "luxon": "^3.7.1"
       },
       "devDependencies": {
         "http-proxy-middleware": "^3.0.0",

package.json

@@ -15,7 +15,8 @@
     "@11ty/eleventy-plugin-syntaxhighlight": "^5.0.2",
     "cors": "^2.8.5",
     "express": "^4.21.2",
-    "fs-extra": "^11.3.1"
+    "fs-extra": "^11.3.1",
+    "luxon": "^3.7.1"
   },
   "devDependencies": {
     "http-proxy-middleware": "^3.0.0",