The behaviour of the calendar is correct. Your event is continuous for all that time. It starts at the start time and ends at the end time, there is no break or gap.
If you have, say, a 3-day event, and want to show it as starting at 8am and finishing at 5pm on day 1, and then the same for day 2 and day 3, then you need to provide the data to fullCalendar as 3 separate events (each with a different date, but the same start/end times).
For example
[
{
"Pressure Equipment Safety Legislation Seminar",
"start": "2019-03-26 08:00",
"end": "2019-03-26 17:00"
},
{
"Pressure Equipment Safety Legislation Seminar",
"start": "2019-03-27 08:00",
"end": "2019-03-27 17:00"
}
{
"Pressure Equipment Safety Legislation Seminar",
"start": "2019-03-28 08:00",
"end": "2019-03-28 17:00"
}
]
Alternatively, depending on which version of fullCalendar you are using, you may be able to take advantage of its recurring event features (new in version 4), or in earlier versions you can implement a custom recurring event solution such as this one.