sorry glen, I am interrupting.earthquakes are tidal force dependent,rather than time dependent.Major quakes(>7.0) can be predicted with fair amount of accuracy(without pin pointing the exact place.
pl see my blog http://earthquake-prediction.blogspot.com/

Here are some thumb rules whereby any one can predict the major earthquakes (>7.0) to fair amount of accuracy
1) find out the date/s when either Jupiter or Saturn is changing the direction from direct to retro gate or vice a versa.
2) 15 days before and 15 days after this date is the window period for major quakes.
3) Moon acts as a trigger in majr quakes ,hence find the date when moon either joins/opposes or squares this planet or Sun.
4)watch out for Full moon and new moon in this window period
5) If both Jupiter and Saturn are changing the direction with in a span of 4/5 days the quake/s would be even more than 8.0
6) magnitude can be fine tuned depending upon proximity of Moon, Jupiter and Saturn.
7) Earth closer to Sun, Moon on equator, aspects of planets can be used to fine tune the magnitude.