diff --git a/calendar.go b/calendar.go
index 59735b6..82118af 100644
--- a/calendar.go
+++ b/calendar.go
@@ -6,10 +6,12 @@ import "git.tebibyte.media/tomo/tomo"
 import "git.tebibyte.media/tomo/tomo/event"
 import "git.tebibyte.media/tomo/objects/layouts"
 
+var _ tomo.Object = new(Calendar)
+
 // Calendar is an object that can display a date and allow the user to change
 // it. It can display one month at a time.
 type Calendar struct {
-	tomo.ContainerBox
+	box tomo.ContainerBox
 	
 	grid tomo.ContainerBox
 	time time.Time
@@ -23,11 +25,11 @@ type Calendar struct {
 // NewCalendar creates a new calendar with the specified date.
 func NewCalendar (tm time.Time) *Calendar {
 	calendar := &Calendar {
-		ContainerBox: tomo.NewContainerBox(),
-		time:         tm,
+		box:  tomo.NewContainerBox(),
+		time: tm,
 	}
-	calendar.SetRole(tomo.R("objects", "Calendar"))
-	calendar.SetAttr(tomo.ALayout(layouts.ContractVertical))
+	calendar.box.SetRole(tomo.R("objects", "Calendar"))
+	calendar.box.SetAttr(tomo.ALayout(layouts.ContractVertical))
 	
 	prevButton := NewButton("")
 	prevButton.SetIcon(tomo.IconGoPrevious)
@@ -48,17 +50,22 @@ func NewCalendar (tm time.Time) *Calendar {
 	calendar.grid.SetRole(tomo.R("objects", "CalendarGrid"))
 	calendar.grid.SetAttr(tomo.ALayout(layouts.NewGrid (
 		true, true, true, true, true, true, true)()))
-	calendar.Add(NewInnerContainer (
+	calendar.box.Add(NewInnerContainer (
 		layouts.Row { false, true, false },
 		prevButton, calendar.monthLabel, nextButton))
-	calendar.Add(calendar.grid)
+	calendar.box.Add(calendar.grid)
 	
-	calendar.OnScroll(calendar.handleScroll)
+	calendar.box.OnScroll(calendar.handleScroll)
 	
 	calendar.refresh()
 	return calendar
 }
 
+// GetBox returns the underlying box.
+func (this *Calendar) GetBox () tomo.Box {
+	return this.box
+}
+
 // Value returns the time this calendar is displaying.
 func (this *Calendar) Value () time.Time {
 	return this.time