Simplify the following text for a Grade 4 native English-speaking person.
Original: Saturday is the sixth day of the week according to international standard ISO 8601 , or the last ( seventh ) day of the week in conventions that consider the week as beginning on Sunday .
Simplified: In some countries , like the United States of America , Saturday is the seventh day of the week . In other parts of the world Saturday is said to be the sixth day of the week .