The type ‘System.TimeZoneInfo’ is defined in an assembly that is not referenced. You must add a reference to assembly ‘System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089’

To fix the error in C# project:
The type ‘System.TimeZoneInfo’ is defined in an assembly that is not referenced. You must add a reference to assembly ‘System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089’

Download and install .Net Framework version 3.5 (If you don’t already have that version).
After installation go into your project and add a reference to System.Core (.Net Tab), make sure the version is 3.5