Aeon418
This was Crowley's idea, based on other ideas and theories popular in his day. But things have moved on since then. (Anthropology in particular.)According to this excerpt, each Thelemic Aeon has a duration of approximately 2000 years - which ties in rather well with the astrological outlook.
The Aeonic model that Crowley invented can be applied to the development of religious ideas, astronomy, procreation, and human consciousness, etc. But linking in to astrological ages and using it to cut history into neat segments is simply wrong headed.
If 1904 marks the beginning of the Aeon of Horus, and you stick with Crowley's idea of 2000 year aeons, then the Aeon of Osiris began in approximately 100BC, and the Aeon of Isis began in approximately 2100BC. Try matching that up with history...... if you can.
Since the boundaries between signs are better established these days (and we're not using tropical astrology either, but actual astronomy), we can safely say that we still be in the astrological age of Pisces until the year 2376 AD. That's rather inconvenient, huh?Also, 1904 as the beginning of the Aeon of Horus is well in keeping with the astrological theory. An exact date for the transition from Pisces to Aquarius cannot be given, however, "Nicholas Campion in The Book of World Horoscopes lists various references from mainly astrological sources for the start of the Age of Aquarius.