I'd like to suggest a new operator for searches and smartlists.

Operator

        currentDay:

Definition

        Filters by current weekday (Monday - Sunday)

Example 1: true if today is Monday-Friday

        currentDay:12345

Example 2: true if today is Saturday-Sunday

        currentDay:67

Example 3: true if today is Monday

        currentDay:1
        currentDay:mon
        currentDay:monday
        currentDay:weekday

Example 4: true if today is Saturday

        currentDay:6
        currentDay:sat
        currentDay:saturday
        currentDay:weekend

Why?

        Task: "Make dental appointment" (tag: onlyWeekdays)

        Smart List: "Next Actions"

                (tag:onlyWeekdays and currentDay:weekday)
                OR (tag:onlyWeekends and currentDay:weekend)
                OR tag:anyDay