Here is a screen shot of the built-in holidays. The Hebrew holidays of Purim and Pesach are also supported (scrolling the screen would display them). All are initially set by default to "Not observed" (i.e. they do not affect your custody schedule). Touch any item in the list to set up if and how it affects your schedule. Additional holidays or yearly events that affect your custody schedule (such as as child's birthday or a state holiday not in this list) can be added via the "New Holiday" menu item.
Spring Break is treated specially in that its date is assumed to vary each year as determined by your child's school and so the starting date must set each year (via the Spring Break menu option) when the date is known.