Date conversion issue from datenum with a few 0's to date

Hi

I ran this formula to extract dates from another table so that i can use that in my datediff function,

Itinerary Created Date = IFERROR(LOOKUPVALUE(Itinerary[Created_DT];Itinerary[Itinerary_Code_CH];Fact_Sales[Itinerary_code_ch]);0)

However, it gave me circular dependacy issues and now i had to write an if error around for those few cases.

Now my other issue is that it returns numbers and as soon as i try and change the date format for my datediff formulat to be able to work, it gives me this error



Can anyone please help me to figure out how i can get pass this

Thanks

Arnoux