Sorry that this is kind of a lazy questions...
I'm curious if $DateTime.Now.Year can be used with NVelocity templates to show the current year? Or do I need to set a variable?
No, as far as I know NVelocity templates only work with objects set in the VelocityContext.
But there is no problem with adding your custom objects to the context and then use them in the template.
_context = new VelocityContext();
_context.Put("your_key", your_object);