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Docs Date Library
FullCalendar leverages MomentJS as its date library. Moment and Duration objects are accepted for many settings and they are used throughout the API.
Moment Object
A Moment object represents a point in time, like the native Date Object, but is far superior.
Duration Object
A Duration object represents a length of time.
Date Formatting Strings
Date formatting strings are used throughout the API and determine how a given Moment object is rendered to a string.
defaultRangeSeparator
The separator text used for date-formatting-string ranges throughout the API.
formatRange
Formats a date range by intelligently inserting a dash between the two dates.