Read about all the changes in v4:
https://fullcalendar.io/docs/upgrading-from-v3
Obscure breaking change from v1->v4 not mentioned elsewhere:
MAX_TIMELINE_SLOTS moved to (packageRoot).config.MAX_TIMELINE_SLOTS
Advancements since latest prerelease:
- Sticky elements while scrolling done with built-in
position:sticky - Bugfixes: #480, #479, #482, #497, #490
NOTE: version "4.0.0" was skipped because of an NPM publishing error