What formula will identify the cell that contains the earliest date and time?

Here is a sample of my spreadsheet:

B2 contains: 2015:12:25 14:01:38
C2 contains: 2016:04:23 06:49:44
D2 contains: 2016:04:23 06:49:44
E2 contains: 2015:12:25 14:43:31
F2 contains: 2015:12:25 14:43:31
G2 contains: 2015:12:25 14:43:31

Note: One to four of the cells in each row may be empty