If you want to convert it into a string with padding for zeros this should work in all cases:
Char(Year(Today())) || "-" || Substr("00", 1, 2 - Length(Char(Month(Today())))) || Char(Month(Today())) || "-" || Substr("00", 1 , 2 - Length(Char(Day(Today())))) || Char(Day(Today()));
Or then you can use something like this which should also work in most of the cases (not sure if JMP will have issue with this specific format on some regional settings):
Format(Today(), "yyyy-mm-dd");
Names Default To Here(1);
dt = New Table("Untitled 3",
Add Rows(0),
Compress File When Saved(1),
New Column("Column 1", Numeric, "Continuous", Format("Best", 12), Set Values([]))
);
dt << Set Table Variable("LastRunDate", Format(Today(), "yyyy-mm-dd"));
-Jarmo