Make totp_timestamp column an integer

README.md

@@ -64,7 +64,7 @@ devise :database_authenticatable, :registerable, :recoverable, :rememberable,
 Then create your migration file using the Rails generator, such as:
 
 ```
-rails g migration AddTwoFactorFieldsToUsers second_factor_attempts_count:integer encrypted_otp_secret_key:string:index encrypted_otp_secret_key_iv:string encrypted_otp_secret_key_salt:string direct_otp:string direct_otp_sent_at:datetime totp_timestamp:timestamp
+rails g migration AddTwoFactorFieldsToUsers second_factor_attempts_count:integer encrypted_otp_secret_key:string:index encrypted_otp_secret_key_iv:string encrypted_otp_secret_key_salt:string direct_otp:string direct_otp_sent_at:datetime totp_timestamp:integer
 ```
 
 Open your migration file (it will be in the `db/migrate` directory and will be
@@ -174,7 +174,7 @@ The following database fields are new in version 2.
 
 To add them, generate a migration such as:
 
-    $ rails g migration AddTwoFactorFieldsToUsers direct_otp:string direct_otp_sent_at:datetime totp_timestamp:timestamp
+    $ rails g migration AddTwoFactorFieldsToUsers direct_otp:string direct_otp_sent_at:datetime totp_timestamp:integer
 
 The `otp_secret_key` is only required for users who use TOTP (Google Authenticator) codes,
 so unless it has been shared with the user it should be set to `nil`.  The

lib/generators/active_record/templates/migration.rb

@@ -6,7 +6,7 @@ def change
     add_column :<%= table_name %>, :encrypted_otp_secret_key_salt, :string
     add_column :<%= table_name %>, :direct_otp, :string
     add_column :<%= table_name %>, :direct_otp_sent_at, :datetime
-    add_column :<%= table_name %>, :totp_timestamp, :timestamp
+    add_column :<%= table_name %>, :totp_timestamp, :integer
 
     add_index :<%= table_name %>, :encrypted_otp_secret_key, unique: true
   end

lib/two_factor_authentication/schema.rb

@@ -25,7 +25,7 @@ def direct_otp_sent_at
     end
 
     def totp_timestamp
-      apply_devise_schema :totp_timestamp, Timestamp
+      apply_devise_schema :totp_timestamp, Integer
     end
   end
 end