Paganism, part 3: the wheel of the year
Most contemporary pagan practice, throughout the UK, US and the antipodes, is based around the central concept of the wheel of the year. Paganism 101 states that this was a focus of ancient Celtic worship; a dubious statement, to say the least, but we might with some accuracy note that it is a focus of pagan worship now, whatever might have been done in the past.
The idea is that every six weeks, on the "quarter days" (solstices and equinoxes) and the so-called "cross quarter days" (the first of February, May, August and November), you hold a ritual or series of rituals to celebrate that particular festival. Some of these are already extant in both folklore and the political and religious calendars: 1 May (Beltane), for example, has traditionally been the focus of a range of celebrations, from fertility to socialism. That's the basic structure, but various paths undertake different practices on top of that: wiccan groups who work with the phases of the moon, for example, or ceremonial magic practitioners who might adopt some of the sacred days of the Egyptian calendar.
Then there are chaos magicians, who work whenever they like and do more or less what they want. Rituals that involve Doctor Who or Buffy rather than Celtic deities? Go for it: chaos magic involves a creative and eclectic approach to popular culture and in many ways it's the cutting edge of magical practice.
http://www.theguardian.com/commentisfree/2013/jul/29/paganism-part-3-wheel-year-dates