diff --git a/web/src/app/sitemap.ts b/web/src/app/sitemap.ts
index 636b0ee8..2a17a1f8 100644
--- a/web/src/app/sitemap.ts
+++ b/web/src/app/sitemap.ts
@@ -1,36 +1,44 @@
-import { BASE_URL, WEB_URL } from "@/constants"
-import { getAllIcons } from "@/lib/api"
-import type { MetadataRoute } from "next"
+import { BASE_URL, WEB_URL } from "@/constants";
+import { getAllIcons } from "@/lib/api";
+import type { MetadataRoute } from "next";
 
-export const dynamic = "force-static"
+export const dynamic = "force-static";
+
+// Helper function to format dates as YYYY-MM-DD
+const formatDate = (date: Date): string => {
+	// Format to YYYY-MM-DD
+	return date.toISOString().split('T')[0];
+};
 
 export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
-	const iconsData = await getAllIcons()
+	const iconsData = await getAllIcons();
 	return [
 		{
 			url: WEB_URL,
-			lastModified: new Date(),
+			lastModified: formatDate(new Date()),
 			changeFrequency: "yearly",
 			priority: 1,
 		},
 		{
 			url: `${WEB_URL}/icons`,
-			lastModified: new Date(),
+			lastModified: formatDate(new Date()),
 			changeFrequency: "daily",
 			priority: 1,
 			images: [`${WEB_URL}/icons/icon.png`],
 		},
 		...Object.keys(iconsData).map((iconName) => ({
 			url: `${WEB_URL}/icons/${iconName}`,
-			lastModified: iconsData[iconName].update.timestamp,
+			lastModified: formatDate(new Date(iconsData[iconName].update.timestamp)),
 			changeFrequency: "yearly" as const,
 			priority: 0.8,
 			images: [
 				`${BASE_URL}/png/${iconName}.png`,
 				// SVG is conditional if it exists
-				iconsData[iconName].base === "svg" ? `${BASE_URL}/svg/${iconName}.svg` : null,
+				iconsData[iconName].base === "svg"
+					? `${BASE_URL}/svg/${iconName}.svg`
+					: null,
 				`${BASE_URL}/webp/${iconName}.webp`,
 			].filter(Boolean) as string[],
 		})),
-	]
+	];
 }