weekday-from-dateTime() function extracts the amount of days (in the week) from a DateTime attribute so it can be used to compare to a value. Values range from 1 to 7 (1 = Sunday, 7 = Saturday).
This query returns all the logs where the amount of weekdays in
DateAttribute is 6 (for example, “Friday 2011-12-30”):
//Logging.Log[day-from-dateTime(DateAttribute) = 6]