You will need to harvest what day of the week Fridays land on. Assuming your weekday starts on Monday:
WeekDay Number = WEEKDAY(Sheet1[Column1], 2)
This would give all your Fridays as 5. From there you can summarize to give out only your Fridays.
MyFridays = CALCULATETABLE(SUMMARIZE(Sheet1, Sheet1[Column1]), Sheet1[WeekDay Number] = 5)
Power BI Super User, Greg Deckler, explains
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