When flying from Bali to Wales, 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 Denpasar Bali Ngurah Rai Airport to Cardiff Wales Airport flight would often be abbreviated as a DPS to CWL flight. While you’re still figuring out your travel plans, it’s not a bad idea to learn the names and codes of other airports around these areas: Swansea Fairwood Comm Airport (SWS), Holyhead Anglesey Airport (VLY).