fix(rc): Fix Version update time parsing failure

src/remote-config/remote-config.ts

@@ -366,16 +366,12 @@ class VersionImpl implements Version {
     // as UTC date strings. If a developer uses a previously obtained template with UTC timestamps
     // we could still validate it below.
     if (typeof version.updateTime !== 'undefined') {
-      if (!validator.isISODateString(version.updateTime) &&
-        !validator.isUTCDateString(version.updateTime)) {
+      if (!this.isValidTimestamp(version.updateTime)) {
         throw new FirebaseRemoteConfigError(
           'invalid-argument',
           'Version update time must be a valid date string');
       }
-      if (validator.isISODateString(version.updateTime)) {
-        // timestamps in output `Version` obtained from the API should be in UTC.
-        this.updateTime = new Date(version.updateTime).toUTCString();
-      }
+      this.updateTime = new Date(version.updateTime).toUTCString();
     }
   }
 
@@ -394,4 +390,8 @@ class VersionImpl implements Version {
       updateTime: this.updateTime,
     }
   }
+
+  private isValidTimestamp(timestamp: string): boolean {
+    return validator.isNonEmptyString(timestamp) && (new Date(timestamp)).getTime() > 0;
+  }
 }

test/unit/remote-config/remote-config.spec.ts

@@ -64,7 +64,7 @@ describe('RemoteConfig', () => {
       email: '[email protected]'
     },
     description: 'production version',
-    updateTime: '2020-06-15T16:45:03.000Z'
+    updateTime: '2020-06-15T16:45:03.541527Z'
   };
 
   const REMOTE_CONFIG_RESPONSE: {
@@ -123,7 +123,7 @@ describe('RemoteConfig', () => {
     versions: [
       {
         versionNumber: '78',
-        updateTime: '2020-05-07T18:46:09.495Z',
+        updateTime: '2020-05-07T18:46:09.495234Z',
         updateUser: {
           email: '[email protected]',
           imageUrl: 'https://photo.jpg'
@@ -135,7 +135,7 @@ describe('RemoteConfig', () => {
       },
       {
         versionNumber: '77',
-        updateTime: '2020-05-07T18:44:41.555Z',
+        updateTime: '2020-05-07T18:44:41.555123Z',
         updateUser: {
           email: '[email protected]',
           imageUrl: 'https://photo.jpg'