If your Gantt is showing a start time that is different than what your activity is or if the activities are not appearing how you think the should, check this setting.

Prior to looking in your schedule for the problem, check the user preferences>resource analysis. Interval for time-distributed resource calculations: Choose the time interval, such as day or week, that you want to use when storing live resource allocation information. Note that, if the layout's timescale interval is set lower than this interval, the calculated amount displays in the first timescale increment. For example, if you set the calculation interval to week and set the layout's timescale interval to day, the total for the week displays on the first day. Refer to the following graphics.