Mod(Year(Date),2000)*10^4
+ Month(Date)*10^2
+ Day(Date)
ps. I should add that the above won’t work for dates prior to 2000, or after 2099. But if you have dates outside that range, then using YYMMDD format is going to break anyway.
If you want something that works for all dates, then I’d recommend YYYYMMDD format, in which case the formula would be:
Year(Date)*10^4
+ Month(Date)*10^2
+ Day(Date)