You are partially right! I'm with you, I don't consider Sunday as the start of the week!!!!
Per Google AI
Sunday is traditionally and legally considered the start of the week in about half of the world's countries, including the United States, Canada, Japan, and India. However, the global perception of when a week begins is actually split into two major perspectives.
The Business Standard: The International Organization for Standardization (ISO 8601) officially designates Monday as the first day of the week.
Global Adoption: Most European countries, parts of Asia, and international business calendars place Monday first.
The Logic: It separates the "weekend" (Saturday and Sunday) cleanly at the end of the week, aligning the calendar with the modern five-day workweek.