Components Share the Same Properties Regardless of Reference Type

Observation

Components are reusable within a citation style, but it is critical to understand that every instance of a component is identical - if you edit a component in one place, every other instance of it will change as well. If you need the same component in different templates, but with different formatting, you must create a separate component for the alternative formatting.

Conversely, this means that if you need the same component formatted identically (for example, the name of a journal in italics), you can define it once and use it in different templates and use cases.
You noticed that the journal article reference type has a comma in front of Year derived. For internet documents you want a period to appear in front of the year. If you change the comma to a period for internet documents in the field Punctuation before for the Year derived component, you'll notice that the period appears for journal articles, too.  

Cause
The journal article and internet document reference types both use the same Year derived component.

Solution
Create a copy of the component. On the Component menu, click Duplicate to  create a component that you can then edit so that it uses different formatting.

Hint

If you're not sure if a component has been used by other reference types, select the component from the list of components on the left side of the Citation Style Editor. Click the Delete button. A warning will appear that shows where else the component was used. Click Cancel.