There's an article circulating on the net claiming that "before patriarchal times" Friday the 13th was a sacred day for women to honor the goddess and to celebrate their menstrual cycles. However, the time period generally considered "before patriarchy" was the stone age in Europe when goddess figurines like the Venus of Willendorf were made, that is, 7,000 BCE to 9,000 BCE, and / or pre-Minoan Crete, before approprixately 3,000 BCE, which was also the stone age. Friday the 13th didn't exist before the application of Germanic derived week names to a Roman-derived calendar system, which did not happen before approximately AD 200.
The "fri" in Friday is from the names of heathen goddesses Freya or Frigga, and the artwork illustrating your article is Freya. These are two of the major goddesses of heathenry, commonly called Norse mythology. The Old Norse calendar had every month starting on Sunday, and every month had 30 days (with some extra days added in the middle of summer) so days of the week didn't change number every month like our calendar does.
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