README.md in unidom-visitor-0.3 vs README.md in unidom-visitor-0.4

@@ -17,10 +17,10 @@
 ```
 
 ## Call the Model
 ```ruby
 phone = PhoneNumberIdentity.create phone_number: '13912345678'
-Unidom::Visitor::User.sign_up phone, 'password', now: Time.now
+Unidom::Visitor::User.sign_up phone, 'password', opened_at: Time.now
 # Sign up a user with given phone number and password
 
 Unidom::Visitor::Guest.valid_at.alive.first
 # Get the first guest