Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Qatar to Normandy as you normally would.
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 Caen Carpiquet Airport flight would often be abbreviated as a DOH to CFR flight. Deauville St Gatien Airport (DOL), Rouen Airport (URO), Le Havre – Octeville Airport (LEH) are other airports near this flight route and their unique identifiers/IATA codes.