These docs are for an old release.
Info on upgrading to v5
themeSystem
Renders the calendar with a given theme system.
String, default: 'standard'
'standard'- Renders a minimal look & feel, the look in most of the demos. Does not require any CSS files beyond the FullCalendar base files.
'bootstrap'- Prepares the calendar for a Bootstrap 4 theme. There are other instructions you must follow to get Bootstrap theming working ยป