Okay,
SELECT Format([Incident_Start]-0.25,"dd/mm/yyyy") AS DateShift, Downtime.Incident_Start
FROM Downtime
WHERE (((Format([Incident_Start]-0.25,"dd/mm/yyyy"))=[Forms]![Downtime_Query]![DateShift])) OR (((Format([Incident_Start]-0.25,"dd/mm/yyyy")) Between...