Google Ad Manager, formerly known as DoubleClick for Publishers or DFP, has its quirks. And some of those quirks relate to what 'start time' will be given to a copy of a line item or a creative. Here's what I mean:
If you copy a line item that has a 'start time' in the past, the 'start time' of the copy is set to the following midnight.
This has caught me out several times. I've created an order to start straight away and copied the initial line item several times (perhaps changing the targeting each time). I've approved everything, only to later find that one line item started straight away and all the others (the copies) waited till midnight.
Conversely if you copy a line item that has a 'start time' in the future, the copy is given an identical start time.
If you go into a line item and copy an active creative, the copy is given the same 'start time' as the original (ie one in the past). However if you copy an inactive creative, its 'start time' will be the current date and time instead.
So to recap - copy a line item, and the start time will either be the following midnight or the same as the original. Copy a creative, and the start time will either be the current date and time or the same as the original! Hopefully this little table makes things clearer:
|If original is...||Then copy has start time of...|
|Line item - start time in past||Following midnight|
|Line item - start time in future||Same as original|
|Creative - active||Same as original|
|Creative - inactive||Current date and time|