This AppleScript service will create a new empty note with the current date and time in ISO 8601 format as its title.
Download this repo as a .zip, open it up, and double-click the “Zettelkasten” file to install it as a service.
You’ll also have the option to assign a keyboard shortcut. I use ⌘⌥Z for the global shortcut and also remap iA Writer’s ⌘N to run it.