PHP dates query malfunctioning : I cannot understand why the following isn't working, and I suspect its something to do with my 'Date' format?

    SELECT * FROM Scans WHERE (Date BETWEEN '$sdate' AND '$edate')

$sdate and $edate are defined dates in format of 01/01/2018. This is also how they are stored in the database under the column 'Date'.

It does fetch information, but between the dates of 01/01/2018 and 16/10/2018 there should be 239 outputs. But for some reason it only shows 137..?

Is my formatting off? When I change 01/01/2018 to 1/1/2018 it then only shows 59 outputs? Pulling my hair out over something so simple - yet difficult things seem to be easy! AAARRRGGH!!

Many thanks in advance.