The day-of-week, such as Tuesday.

This represents the standard concept of the day of the week. In the default ISO calendar system, this has values from Monday (1) to Sunday (7). The DayOfWeek class can be used to interpret the result.

Most non-ISO calendar systems also define a seven day week that aligns with ISO. Those calendar systems must also use the same numbering system, from Monday (1) to Sunday (7), which allows DayOfWeek to be used.

Calendar systems that do not have a standard seven day week should implement this field if they have a similar concept of named or numbered days within a period similar to a week. It is recommended that the numbering starts from 1.