In excel, I need to find the maximum date based on the employee number - excel

Question

I have tried to use the following formula when trying to find the max date of these columns based on the employee number in my hundreds of thousands lines of data. The formula bar gives me 'yes' when it is the max, however in my cell it says 'no'. I cannot figure out what the issue is. Thanks for the help.
Tamara
Excel Max date formula Image
Formula used: =IF(AQ2=MAX(IF($C:$C=C2,$AQ:$AQ)),"YES","NO")
A B Employee Number Max?
11-Mar-13 12-Mar-13 199 NO
24-Mar-13 26-Mar-13 199 NO
1-Aug-13 6-Aug-13 199 NO
22-Dec-13 27-Dec-13 199 NO
15-Apr-13 17-Apr-13 206 NO
18-Apr-13 18-Apr-13 206 NO
8-Aug-13 10-Aug-13 206 NO
17-Oct-13 18-Oct-13 206 NO
25-Dec-13 20-Feb-14 206 YES
8-May-13 8-May-13 214 NO

Answer 1

You can also accomplish this without an array is all of the dates for a specific employee ID are unique--that is, you won't have two of the same date. In this case, the following formula will check that (a) the number of dates with employee ID is equal to (b) the number of dates with employee ID that are less than or equal to the current employee ID. This will only be true for the "max" date for said employee id:
=IF(COUNTIFS($C:$C,C2)=COUNTIFS($C:$C,C2,$A:$A,"<="&A2),"Yes","No")

Answer 2

If I understand your question correctly, you want to find the set of dates with the largest time span in between said dates. If this is the case, then I would recommend using two seperate fucntions, the =DAYS360 function and the =MAX function.
I have re-created your sheet and it will end up looking similar to this:
Here is the same picture of the same sheet with functions revealed, so that you can see how the functions are used:
The =DAYS360 function takes two inputs, and return the number of days in between two dates. The max function simply finds the largest number in a range. Please let me know if this helped.
EDIT: Also, if you want to see the actual word Max next to the largest date range, you can nest the Max fucntion from my column E within an If function, like this:
=IF(MAX(D:D)=D2,"Max","")

Answer 3

If I understand you correctly, do you want "YES" to appear for each employee's max date range? Assuming column AQ contains the spans between dates in columns A and B (i.e. =B2-A2 copied down), your formula should work.
This only works as an array formula, so make sure you press CTRL+SHIFT+ENTER when entering the formula, then copy it down to all cells in the same column.
=IF(AQ2=MAX(IF($C:$C=C2,$AQ:$AQ)),"YES","NO"), entered in D2 using CTRL+SHIFT+ENTERand copied down produces the following:
A B C D ... AQ
11-Mar-13 12-Mar-13 199 NO 1
24-Mar-13 26-Mar-13 199 NO 2
1-Aug-13 6-Aug-13 199 YES 5
22-Dec-13 27-Dec-13 199 YES 5
15-Apr-13 17-Apr-13 206 NO 2
18-Apr-13 18-Apr-13 206 NO 0
8-Aug-13 10-Aug-13 206 NO 2
17-Oct-13 18-Oct-13 206 NO 1
25-Dec-13 20-Feb-14 206 YES 57
8-May-13 8-May-13 214 YES 0
If you are simply looking for the greatest date range, the formula =IF(E2=MAX($E:$E),"YES","NO") entered in D2 and copied down will do the trick.