Format Date

How do you determine that the value should end in 21?

If the value is in A1 use =left(A1,8) to get the correct number of digits for a date. If this value is in B1 then you can use the following to get the date serial number which you can format to the date presentation that you want.

Formula:

=DATE(LEFT(B1,4),MID(B1,5,2),RIGHT(B1,2))