Different ETF timing systems use different logics and parameters. Some may track prices on a daily or monthly basis.
For a volatile market like ETF, tracking the price movement with such systems is more efficient than tracking manually. Once deployed, these systems study the ETF progress and indicate the most feasible transactional activity.
The various ETF timing systems available in the market are:
Weekly ETF timing systems: Such timing systems trade once in the week at the most. They use momentum shift as the parameter for choosing the best ETFs to buy or sell. Each has its own set of ETFs that it tracks.
Monthly ETF timing systems: These timing systems trade once in a month or none at all. They track a large number of ETFs and trade with the three best ETFs. It works by comparing the past performance of the ETFs at the same time of the month. If it finds an ETF performing better than the historical average than the system undervalues it and picks another ETF or vice versa.
No matter how smart the ETF timing systems get, they are still computer programs that are designed with tried and tested techniques. The ETF market, like the market that it trades in, is highly volatile. So, no one can predefine its behavior.
There are many factors that decide the behavior which can not be tracked statistically like:
Emotions
Rumors
Dynamically changing preferences
The best way to use the ETF timing system is to combine its results with other indicators and thus, identify the best buy. ETF timing systems, at times, lose out due to its stringent adherence to parameters.
However, there is a consensus that due to the volatility that the market has, it is important to use some sort of timing system that is more yielding than the conventional buy and hold strategy.