The time frame that you use to study charts depends on your trading horizon. If you are a short-term trader who looks at end-of-day charts and have a trading horizon of less than a year, you should be using daily charts for trading. If your trading period is longer than one year, you are better off using weekly charts, which help study the market from a longer-range perspective.
Traders usually concentrate on charts made up of daily and intraday data to forecast short-term price movements. The shorter the time frame and the less compressed the data is, the more detail that is available. While long on detail, short-term charts can be volatile and contain a lot of noise. Large sudden price movements, wide high-low ranges and price gaps can affect volatility, which can distort the overall picture.
Investors usually focus on weekly and monthly charts to spot long-term trends and forecast long-term price movements. Because long-term charts cover a longer timeframe with compressed data, price movements do not appear as extreme and there is often less noise.
However, it is always best to use more than one time frame for analyzing charts. If you use daily charts for trading it would be helpful to also look at weekly charts, which help identify support and resistance levels and the direction of the major trend.