please help me with ensuring DEFAULT DATE is entered in correct format in = IFNA(VLOOKUP(..), DATE..

...set-up or scenario

some text in the date fields are as correct in date format and some are inserted as TEXT format. These came from trying to insert a default date when a vlookup did not find suitable result in the lookup table.

=IFNA(VLOOKUP([@[uniq_line_item]],saved_promise_date_hard[#All],2,FALSE),"1/1/1900")

the thing is if the item being looked (uniq_line_item) exists in the look up table (saved_promise_date_hard) but there is no promised date ie blank then it returns the default value (1/1/1900) value in date format

but if the item being looked (uniq_line_item) DOES NOT EXIST in the look up table (saved_promise_date_hard) then default value (1/1/1900) returned is in text formatted of the default

My question would be how could I write this better that the default value entered is a date and not text. 

Thank you in advance