Why does a french calendar start on a Monday?

The French calendar starts on a Monday due to the influence of the ISO 8601 standard, which designates Monday as the first day of the week. This choice aligns with many European countries and reflects a cultural preference for organizing the workweek. Additionally, starting the week on a Monday helps to provide a clear distinction between weekdays and the weekend. The French Revolution also contributed to various reforms in calendar systems, but the Monday-start convention has persisted.