When flying from Doha to Rochester, New York, the time of day you decide to fly out makes little to no difference towards the overall price you’ll pay on tickets.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Doha Hamad Intl Airport to Rochester Greater Rochester Intl Airport flight would often be abbreviated as a DOH to ROC flight.