Much about a person's efficiency, ability and character can be determined from his punctuality. Every person seems concerned about his own time, comfort and convenience, yet we tend to be inconsiderate of the time comfort and convenience of others by arriving late or not informing a person of our absence.
By keeping one's appointments and being punctual in ones duties one will be fulfilling the call of the Quran in Surah Al-Isra' V.34 “and keep your promises. The promise will be questioned about.”
Once, Rasulullah (Sallallahu Alaihi Wasallam) gave an appointment to a certain person. However, the person came three days later. Rasulullah (r gently reprimanded him 'You have caused me some trouble. I have been expecting you since three days.' (Sunan Abi Dawood)
Technology has made it easy for us to communicate swiftly with the opposite party if we are delayed or cannot meet the required date or time. Islamic etiquette requires us to inform people accordingly if and when we are unable to meet our obligations.