diff --git a/src/components/input-time-picker/input-time-picker.e2e.ts b/src/components/input-time-picker/input-time-picker.e2e.ts
index e0a94d86051..c510293ecc4 100644
--- a/src/components/input-time-picker/input-time-picker.e2e.ts
+++ b/src/components/input-time-picker/input-time-picker.e2e.ts
@@ -33,6 +33,18 @@ describe("calcite-input-time-picker", () => {
     renders(`<calcite-input-time-picker lang="en-us"></calcite-input-time-picker>`, { display: "inline-block" });
   });
 
+  describe("renders with base lang when region code is unsupported", () => {
+    renders(`<calcite-input-time-picker lang="nl-nl"></calcite-input-time-picker>`, { display: "inline-block" });
+  });
+
+  describe("renders with pt-PT locale", () => {
+    renders(`<calcite-input-time-picker lang="pt-PT"></calcite-input-time-picker>`, { display: "inline-block" });
+  });
+
+  describe("renders with no locale", () => {
+    renders(`<calcite-input-time-picker lang="no"></calcite-input-time-picker>`, { display: "inline-block" });
+  });
+
   describe("honors hidden attribute", () => {
     hidden("calcite-input-time-picker");
   });
diff --git a/src/components/input-time-picker/input-time-picker.tsx b/src/components/input-time-picker/input-time-picker.tsx
index 2123eae53f8..ed0f062879d 100644
--- a/src/components/input-time-picker/input-time-picker.tsx
+++ b/src/components/input-time-picker/input-time-picker.tsx
@@ -62,6 +62,7 @@ import localeData from "dayjs/esm/plugin/localeData";
 import localizedFormat from "dayjs/esm/plugin/localizedFormat";
 import preParsePostFormat from "dayjs/esm/plugin/preParsePostFormat";
 import updateLocale from "dayjs/esm/plugin/updateLocale";
+import { getSupportedLocale } from "../../utils/locale";
 
 // some bundlers (e.g., Webpack) need dynamic import paths to be static
 const supportedDayJsLocaleToLocaleConfigImport = new Map([
@@ -555,18 +556,22 @@ export class InputTimePicker
   };
 
   private async loadDateTimeLocaleData(): Promise<void> {
-    const normalizedLocale = this.getNormalizedLocale();
+    let supportedLocale = getSupportedLocale(this.effectiveLocale).toLowerCase();
 
-    if (normalizedLocale === "en" || normalizedLocale === "en-us") {
-      return;
+    if (supportedLocale === "no") {
+      supportedLocale = "nb";
+    }
+
+    if (supportedLocale === "pt-pt") {
+      supportedLocale = "pt";
     }
 
     const { default: localeConfig } = await supportedDayJsLocaleToLocaleConfigImport.get(
-      normalizedLocale
+      supportedLocale
     )();
 
     dayjs.locale(localeConfig, null, true);
-    dayjs.updateLocale(normalizedLocale, this.getExtendedLocaleConfig(normalizedLocale));
+    dayjs.updateLocale(supportedLocale, this.getExtendedLocaleConfig(supportedLocale));
   }
 
   private getExtendedLocaleConfig(
@@ -644,22 +649,6 @@ export class InputTimePicker
     }
   }
 
-  private getNormalizedLocale(): string {
-    const { effectiveLocale } = this;
-    let normalizedLocale = effectiveLocale ? effectiveLocale.toLowerCase() : "en";
-
-    if (normalizedLocale === "en-us") {
-      normalizedLocale = "en";
-    }
-    if (normalizedLocale === "pt-pt") {
-      normalizedLocale = "pt";
-    }
-    if (normalizedLocale === "no") {
-      normalizedLocale = "nb";
-    }
-    return normalizedLocale;
-  }
-
   onLabelClick(): void {
     this.setFocus();
   }
@@ -765,8 +754,6 @@ export class InputTimePicker
   connectedCallback() {
     connectLocalized(this);
 
-    this.effectiveLocale = this.getNormalizedLocale();
-
     if (isValidTime(this.value)) {
       this.setValueDirectly(this.value);
     } else {