I received the following error creating a formula within the Visual Flow formula editor after selecting he 'Check Syntax' button:

The formula expression is invalid: Syntax error. Missing ')'

For the following statement:

IF ( {!$Record.Date_Time_Field_1__c} < 14:00:00, {!$Record.Date_Time_Field_1__c} + 04:00:00, {!$Record.Date_Time_Field_2__c} )

This seems fairly straightforward so I am hoping someone can shed some light. Am I missing something related to the Visual Flow formula editor, $Record placeholders or Date/Time values here that results in the error?