The more you speak to the veterans in the industry, the more they talk about cycles and intervals. Recently, Tom McClellan of McClellan Oscillator was in Calgary to speak. He spoke of cycles and time shifted intervals. Cycles indicate a repetitive low - low pattern. Time interval theory suggests that time interval (eg 15 months) is important, but it may be a meaningful high or low. George Lindsay use time intervals that ended up spotting an exact date where multiple time intervals would converge and create a strong decision point on the charts. I spoke with Martin Pring this week and his use of cycles is very detailed. Ron Miesels is a Canadian chartist who uses phases and cycles. Lets go check some intervals out on an $SPX chart.
Here is the $SPX.