What is the difference between "dddd, dd/MM/yyyy HH:mm:ss" and "dddd, dd/MM/yyyy HH:MM:ss"

Hi,

I have one value= 05/02/2013 00:00:01

When I am converting this value to date I am getting different output.

CDate(txtstart.Text).ToString("dddd, dd/MM/yyyy HH:mm:ss")

Output- Tuesday, 05/02/2013 00:00:01

CDate(txtstart.Text).ToString("dddd, dd/MM/yyyy HH:MM:ss")

Output- Tuesday, 05/02/2013 00:02:01

Whai is the difference between "dddd, dd/MM/yyyy HH:mm:ss" and "dddd, dd/MM/yyyy HH:MM:ss"?

Thanks in advance.