A lot of what is "best" has to do with how specific you want to be. Appending "every" to a date is great if you want something to occur every N. But what if you want it to occur every other N? Or the first N of every M? There's a reason why things like Crontab or iCalendar's RRULE are so specific and verbose.

In order to decide what is "best" I would first decide how specific I needed to be and then start to narrow my input options based on my defined need.