How to enter Seconds into Datetime fields using the standard UI

Say you have a datetime field Start__c on a pagelayout.

Now try to enter a date (we have DE locale enabled, but should be similar in EN):

• 31.08.2014 14:53 ==> works
• 31.08.2014 14:53:38 ==> doesn't work

The only way I found is to set it programmatically via APEX.

What is the easiest way to deal with Seconds using as much of Standard Functionality as possible?

Is there a feature to enable Seconds for Datetime? (Possibly even Milliseconds?)

The datetime field is perfectly capable of carrying Seconds in the database. However when it comes to calculations, Seconds seems again to be second-class citizens: Duration as difference betweed to Datetime fields does not respect Seconds

Finally I come back to Milliseconds:

Is the best we can do to track them in a separate field like StartMilliseconds__c (number) in addition to Start__c (datetime)?