Using datetime for larger period of data

What a great tutorial!

I have looked everywhere but could not find an answer for this problem.
I have more than one day of data. The grapics starts over at the left side as there is the time 00:00

Now, how can I use the date and time for the hAxis? 
If I simply add a row “datetime” I get an error “invallid type”.

Can you please help me?