slashes of both kinds are used in directory and regexps... hypenating dates makes life a little easier for the programmer...
also it is easier for the programmer to put a 0 in front of the month or the day that is less than 10... presumably many programmers have worked with applications using dates and find it easier to do a 6 or 8 digit string... like today would be 11092001... a 1192001 would be unreadable by the computer
programmers also probably have had a lot of grief working with the lowercase l and the number 1... it wouldn't surprise me if the guy puts a slash inside the number zero, either for readability. I do that myself sometimes.
as for the block handwriting... he may just have been covering up his regular handwriting by writing in all caps.