Daylight Saving nightmare

Based on your process explanation, i think that it is somewhat flawed - but anyway good luck with that. Still robocopy could be used - be it one or several backups from same source - and that is a fact. No need to write a 'specific program' to handle backup task - even when there is a need to 'opt in' files to backup. Powershell script can handle that.

Hardware changes detection is quite straightforward, one just needs to handle Win32_VolumeChangeEvent.

For unmounting one could use powershell WMI script or fex. using devcon.exe utility can perform usb device unmounting.

https://blogs.technet.microsoft.com/...ets-connected/

https://msdn.microsoft.com/en-us/lib...(v=vs.85).aspx