These docs are for an old release.
Info on upgrading to v5
displayEventTime
Whether or not to display the text for an event’s date/time.
Boolean
This setting only applies to events that have times (allDay equal to false). If set to true, time text will always be displayed on the event. If set to false, time text will never be displayed on the event.
Events that are all-day will never display time text anyhow.
When this setting is not specified, the default that is computed is based off of the current view. For example, time text will be displayed in all DayGrid, and TimeGrid views by default. For timeline views, it depends on the duration.