The start of the week depends on cultural and regional differences. According to the international standard ISO 8601, Monday is considered the first day of the week. This is the prevailing standard in most European countries and many other parts of the world. However, in countries like the United States, Canada, and several countries in North and South America, Sunday is commonly regarded as the first day of the week. Additionally, some countries in the Middle East start the week on Saturday. In sum, the week can officially start on Sunday, Monday, or Saturday depending on the location, but Monday is the recognized international standard start of the week.