The Cross-quarter day reference article from the English Wikipedia on 24-Apr-2004
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Cross-quarter day

1. See quarter days.

2. In the Neopagan wheel of the year, there are eight solar holidays or sabbatss. Of these, four (Yule, Ostara, Midsummer and Mabon) refer to the solstices and equinoxes. The other four fall between these, and are referred to as cross-quarter days.

The cross-quarter days are:

They are usually celebrated on the evening before.