The WeekdayMask allows you to get or set the weekday selection, without selecting individual days using GetWeekday(Weekday) and SetWeekday(Weekday,Boolean). The WeekdayMask is a bit mask, with bits 1-7 representing days 1-7 (Sunday is day 1; Saturday is day 7).
For example, to select Saturday and Sunday you would set bits 1 (=0x2 or binary 10) and 7 (=0x40 or binary 1000000), so the WeekdayMask would be set to 0x42 (binary 1000010). To select all days of the week, set the WeekdayMask to ArcanaDevelopment.adTempus.Shared.SpecialMaskValues.AllDaysOfWeek.