Staple binding is how traditional calendars are printed. These calendars are printed as a stapled (saddle-stitched) booklet where pages must be in multiples of 4.

Unlike stapled calendars, spiral bound calendars can be printed with any amount of pages. Making this the more flexible calendar option, although less traditional.

Wire-O bound calendars are very similar to spiral calendars but are assembled with a metal wire instead of a plastic coil. They tend to lay more flat and have better registration across the gutter / binding area.