Placeholder for year only?

I’m using the placeholders listed in “help” on the text page, thanks! However there doesn’t seem to be an obvious option for formatting the date. For example I’d like to just have the year, not the whole date. The help section says “see general settings for date format” but I don’t want to change my whole website to using year-only dates. Are there any options for adding a %date-yyyy% placeholder? are there any hooks I could use in functions.php for example to extend the placeholder function in your code? thanks!