The Jewish Sabbath is from Friday sundown until Saturday after twilight. That is the seventh day of the Jewish week. See also:More about the Jewish Shabbat.
Saturday
Week calendar is a calendar displaying one week in a template.
The ISO calendar is primarily a fiscal calendar and does not change the names of the days of the week, although it does number them differently, starting with 1 on Monday and ending with 7 on Sunday, however Monday on the ISO calendar is also the same Monday on the Gregorian calendar (day 2) and the same Monday that is on the Jewish calendar. Shabbot (or Saturday) does not change. It is still on the same day. But all that is really not relevant, as the keeping of Shabbot is based on the command in the Torah which is based on the Hebrew calendar. So it would not matter what calendar was in use by any country, even if it did mess with the definition of the week, the Hebrew calendar remains the same.
1 week = 1 week on the Hebrew calendar. (The Hebrew week is the same length as the week on the Western calendar)
Saturday is the seventh day of the week.
Different webaites provide option to display week number in calendar.
Thursday is the fifth day of the week in a North American calendar.
Apple does not provide templates for it's official calendar app on the current and upcoming iPhone operating systems. There is an app called "Week Calendar" that provides templates for its calendars ($1.99).
In the Old Testament of the Bible - which is a Jewish book - God made the world in 6 days and rested on the seventh. This rest day, the last day of the week, was Saturday, and became the Jewish sabbath. Jesus was crucified on a Friday and rose again on the Sunday. Christians keep Sunday as their holy day. This does not change the fact that Sunday is the FIRST day of the week The modern habit of considering Sunday the last day of the week has arisen since the adoption of the word WEEKEND to mean Saturday and Sunday. This does not change the fact that Sunday is the FIRST day of the week
The seventh day of the week is Saturday, as is shown on nearly every calendar made. (If you're confused about the Sabbath... yes, that's Saturday, and by Jewish tradition it begins at sunset of the previous day (Friday). Any references to Sunday as the Sabbath are ignoring tradition and linguistics. The early church referred to Sunday as "the Lord's day" while still recognizing that it was not, in fact, the Sabbath.)
In English, "Saturday" is the seventh day of the week. There is no other answer. "Friday" is the last day of the "work week", but a "work week" is only five days.