"First day of week", as shown by calendars in general use, is different depending on country. Example:
(Monday) versus (Sunday).
What is its meaning/use in countries where English is an official language (e.g. USA, UK, New Zealand, Australia, India, South Africa, Malta, Ireland, Canada)?
I am looking for an answer similar to
"In [country] it is Monday, whereas in [country] it is Sunday. Also in [country] it is Sunday, while in [country] it is Monday. ..."
Thus, maybe just take a look at your calendar and tell me what you see (and where you are located).
Related: http://www.tondering.dk/claus/cal/week.php, "What is the first day of the week?" (which neither gives a list).