It's not clear how "weekend" is defined. In some companies, Saturday is a working day, so not strictly speaking a weekend for all persons.
This is also seen in https://github.com/date-fns/date-fns/issues/2085.
Suggested edits
I would suggest adding the information that Saturday and Sunday are considered weekend days and those are the only ones checked in this utility.
There is an issue with the isWeekend documentation
The problem with isWeekend documentation
It's not clear how "weekend" is defined. In some companies, Saturday is a working day, so not strictly speaking a weekend for all persons. This is also seen in https://github.com/date-fns/date-fns/issues/2085.
Suggested edits
I would suggest adding the information that Saturday and Sunday are considered weekend days and those are the only ones checked in this utility.