The best time frame for day trading is a question that is overlooked by many traders. It defines how you trade and the methods you use to trade. Have a successful trading method in one time frame may not translate to another time frame easily. It would be as if a trader who only works on the 1 minute charts switching to a daily outlook and expecting the same results.
Why choose one set of time frames to trade?
The real answer is that there is no best time frame for day trading. The most important aspect of choosing a time frame for day trading is that you stick with a single set. Swapping between 3 or 5 different time frame sets will not give you good trading results. You may even have a successful trading method, in hand, but swapping time frames is ruining your trading results.