1) I've seen calendars with both starting days (Sunday/Monday). Anecdotally, calendars with Sunday as the first day seemed to be more popular when I was a kid; now, calendars with Monday as the first day seem to be more common.
2) The 12-hour system is far more popular here than the 24-hour system. Not that we don't use it, but in my experience, 24-hour tends to be mainly used in professional settings; 12-hour is used essentially everywhere else.
1) I've seen calendars with both starting days (Sunday/Monday). Anecdotally, calendars with Sunday as the first day seemed to be more popular when I was a kid; now, calendars with Monday as the first day seem to be more common.
2) The 12-hour system is far more popular here than the 24-hour system. Not that we don't use it, but in my experience, 24-hour tends to be mainly used in professional settings; 12-hour is used essentially everywhere else.