Forgot to say that you could schedule an API workflow to first do the reset and then update the stored date (in that order), so you don’t have do it manually. You’d have the stored date = current date condition as just an extra check on the conditions, it’s not really necessary.
I haven’t done a scheduled API workflow myself but I think others have found success (not sure what account plan you’re on or if that matters either):
Also with your initial solution, consider the scenario where you only have one March post at the top (with March still being the current month), then it somehow gets deleted. Then your workflow is going to get triggered again, even though you already ran it (if this is a workflow that isn’t manually triggered).
Your other solution (when current date time > store date = trigger workflow) also doesn’t look ideal, wouldn’t you be triggering your workflow multiple times then, unless you are are manually triggering this?