These docs are for an old release. Info on upgrading to v4
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getDate

Returns a Moment for the current date of the calendar.

.fullCalendar( ‘getDate’ ) -> Moment

For month view, it will always be sometime between the first and last day of the month. For week views, it will always be sometime between the first and last day of the week.

Example of displaying a calendar’s current date when a button is clicked:

$('#my-button').click(function() {
  var moment = $('#calendar').fullCalendar('getDate');
  alert("The current date of the calendar is " + moment.format());
});