These docs are for an old release.
Info on upgrading to v5
allDayDefault
Determines the default value for each Event Object’s allDay property when it is unspecified.
Boolean, default: undefined
By default, allDayDefault is not set. As a result, any Event Objects that do not specify an allDay property will be subject the guessing behavior mentioned in the Event Object article.
Set this option to true or false to make it affect Event Objects without an allDay property.