Custom work hours in the SharePoint Date & Time Field

Hello everyone,

I want to be able to customise the selectable hours within the time drop down of a Date & Time column. E.g. The drop down starts at 08:00 instead of 00:00 and ends at 18:30 instead of 23:59. See the attached screenshot for further clarity on what I’m referring to.

(I apologise for the image quality. As I have had to log into my personal account to post, I have had to take a picture of the screen rather than screenshot)

I am creating an annual leave request system via SharePoint Lists, Outlook, & MS Power Automate. After much faff, everything is set up and working. However, as the End Date automatically pre-populates 00:00 which has resulted in some users leaving the end date time at 00:00 which means the system doesn’t count them as being on leave at all that day.

I hope this makes sense, it has been difficult for me to articulate it properly. 

Thank you