Date difference Average

[kashyap]

I have 2 column as below and I want to calculate the average number of days
ABC occurs.. In this case it should be 3.33

Col A Col B
01-Apr ABC
01-Apr DBA
01-Apr ABC
03-Apr GRT
05-Apr HTA
05-Apr JYU
08-Apr ABC
08-Apr GRT
08-Apr HTA
10-Apr JYU
11-Apr ABC

 

[barry houdini]

You could also try this formula

=(MAX(IF(B2:B12="ABC",A2:A12))-MIN(IF(B2:B12="ABC",A2:A12)))/MAX(COUNTIF(B2:B12,"ABC")-1,1)

confirmed with CTRL+SHIFT+ENTER