>Remarks
>
> SYS(3) may return a non-unique name when issued successionally on a fast computer. Use SUBSTR(SYS(2015), 3, 10) to create unique, legal eight character file name.

They are legal file names; there is no OS restriction on file names that begin with a numeral. However, VFP internal names like aliases are not file names, and there is a specific statement that VFP names need to start with an _ or alpha character. OS file name restrictions are not identical.