How to fix auth/invalid-creation-time: Creation time must be valid UTC date string in Firebase

What this error means

The error indicates your application is trying to set a user's creationTime field with a value that doesn't conform to Firebase's required UTC date format.

Typical symptoms

• Firebase Admin SDK throws error when calling createUser() or updateUser()
• User migration scripts fail with timestamp validation errors

Common causes

1. Providing a non-UTC timestamp string
2. Using local time format instead of UTC

How to fix "auth/invalid-creation-time: Creation time must be valid UTC date string"

Advanced notes

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Official resources & further reading

• 📚Firebase Official Documentation
• 📖
  Firebase Admin SDK - Create a User(Official Docs)