Monday is the first day of the week according to ISO 8601 (an international standard covering the worldwide exchange and communication of date and time-related data.)
Sunday is the first for *some* countries is because of religious reasons. For those of Christian ~~and Jewish faith~~, sunday is the most important day of the week, though in the United States, Monday is considered as the **first day of the work week for logistic purposes** such as companies paying their employees
it’s monday everywhere for work/business/logistics purposes.
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