I've a flight RDU-DFW-NRT-SIN upcoming soon. The first flight is leaving in the early morning. Now something has popped up at work and I'll need to be on a call at the time of that RDU-DFW leg. Is it generally possible to move that initial flight to the night before, so my connection time of 3 hours becomes more like 12-14 hours? Or would that require separate tickets?