You can put anything you like in your logbook - it is your personal record. The problem comes when you are submitting hours for the issue or re-validation/renewal of a licence or rating when the issuing Authority will have its own rules regarding what may and may not be counted. For example, you can log hours spent as a safety pilot but, in the UK you cannot claim them as experience towards the issue of an ATPL whereas in the US you can.
I'm not sure why you would want to log landings (except as a personal record) - I can't think of any experience requirement that includes number of landings other than for the issue of a type rating, in which case it is only landings on the type that count.