How are prayer times calculated according to Tawqeet al-Ghuroobi (sunset-based timing), and how is sunset always at 12 o'clock, knowing that the time of sunset changes daily?

Prayer times are not calculated by a specific time in hours, due to their variation from month to month and from country to country. Rather, they are calculated by the شرعية (Shari'ah-compliant) signs. Nevertheless, the time of each prayer can be determined by the غروبي (maghribi) timing, by comparing it with the زوالي (zuhr/noon) timing and knowing the difference in hours between them.