Calculate average time from latest date average

[novice1]

I want to calculate the average time from the latest date of the table. My table looks like this.

datetime                                 date                   time

01/01/2008 03:23:45              01/01/2008        00:03:56

01/01/2008 04:20:45              01/01/2008        00:02:15

01/01/2008 01:23:45              01/01/2008        00:01:56

01/01/2007 03:23:45              01/01/2007        00:03:56

01/01/2007 03:23:45              01/01/2007        00:03:56

01/01/2007 03:23:45              01/01/2007        00:03:56

I want to display as average time for 01/01/2008 by calculating the average time taken from 3 valuses from time column.

Avg Time : 00:02:13 (from latest date)

any help is appreciated. thanks