Most printed birthday calendars are to big. This one uses normal paper format.
Prepare 12 pages, one for each month. The page has the name of a month and on every page are the numbers of the days of that month, 1-31 (use 2 columns).
Insert two holes on top of all pages ( use a two hole punch )
Use a bit of string to connect the pages (image). The string connects the pages and is used to hang the calendar.
Write all birthdays in correct places.
Hang you calendar on a nail, a drawing pin or thumb tack. Flip the pages until the right month is in view.
Use coloured paper and add pictures