These docs are for an old release. Info on upgrading to v6
edit doc

defaultRangeSeparator

The separator text used for date-formatting ranges throughout the API.

String, default: ' - '

This calendar-wide setting affects settings that render date ranges, like eventTimeFormat. The default will look something like 2:00pm - 3:00pm.

If you want to customize the title in the toolbar, use titleRangeSeparator instead.