Calendar event resize and move adjusts times by one hour

Wappler: v3.9.6
MacOS
PHP

I’ve come across something strange. I have the events working well and can select a time period and it returns the correct start/end date/time but if I resize or move the event, the time returned is one hour less than it should be. The variables are identical in all three - Event Drop/Move, Event Resize and Select but only Select is returning it correctly.

    dmx-on:select="varShowEditColumn.setValue(1);formAddEditVisit.inp_visitDateTime.setValue($event.event.start.substr(0, 16));formAddEditVisit.inp_visitEndDateTime.setValue($event.event.end.substr(0, 16));connSelectedVisit.reset();formAddEditVisit.inp_VisitID.setValue(0)"
    					dmx-business-hours.businesshours="{startTime:'08:00',endTime:'18:00',daysOfWeek:[1,2,3,4,5]}" business-hours="true" dmx-constraint=""
    					dmx-on:eventresize="varShowEditColumn.setValue(1);formAddEditVisit.inp_visitDateTime.setValue($event.event.start.substr(0, 16));formAddEditVisit.inp_visitEndDateTime.setValue($event.event.end.substr(0, 16))"
    					dmx-on:eventdrop="varShowEditColumn.setValue(1);formAddEditVisit.inp_visitDateTime.setValue($event.event.start.substr(0, 16));formAddEditVisit.inp_visitEndDateTime.setValue($event.event.end.substr(0, 16))">

The substr is there as that’s the only way I could get dates and times correctly into a type="datetime-local" input.

I’m in the UK which is now in British Summer Time so we’re an hour ahead of GMT so is that what’s causing it? If so, why is dmx-on:select working correctly?