Celebrating the quarter and cross quarter days can work for atheists, science fans and Pagans alike. You get a holiday every month and a half. You can simply celebrate the changing of seasons/Earth’s relative position to the Sun or get all magick with it, as you like. The quarter days are the solstices and equinoxes, the cross quarter days are the points in between. Halloween (Samhain) and May Day (Beltane) are the famous cross quarter days, but they happen in winter (Imbolc, Feb 1- also known as Groundhog Day) and summer (Lammas/Lunasa, Aug1).