How to order by time in a day using DATETIME

[t_machine]

Hi, I have a table that stores each record with in a DATETIME column. I was wondering how accurate is it to order by the date column

 

Example

$sql = "SELECT * FROM table_name WHERE {get todays result} ORDER BY date_column DESC";

 

Would an order like that display the results for the day correctly, and would it list the last result for the day first?

 

Thanks for any help

[Mchl]

If it's DATETIME it's accurate to one second.