which time frame is best for day trading?

Good one George, for me I would say every time frame is important to a day trader. Just because one is day trading doesn't mean to only stick to minute time frames.

The support or resistance level you are looking for may be connected to yesterdays price, so how else will you find it if you don't zoom out to the daily time frame? sure, you can use technical indicators but is simpler to just zoom out to a higher time frame.

I use all time frames when day trading and when price is on a sustained bull run, I even zoom out as far as the daily time frame to help me find out where the bull run is going to end.

When day trading I use the minute time frames and I also use the TradingView or MT5 platforms because they offer more timeframe options than MT4.

Although I focus more on minute timeframes, every once in a while I still glance at the higher timeframes to get a bird's eye view of the market landscape.