Changing the Time Graph
Above the time graph, there is a Graph by feature that lets you graph your data by hour, day, week, or month so you can analyze trends according to the selected view. Hourly graphs are also available for some reports.
This option is displayed if hourly reporting is available for that report For example, if you navigate to the Audience Overview report, you see an option to view the graph by hour. With this option, you see 24 data points, one for each hour of the day.
This is the default view for your graphs, and shows daily values for the date range.
A week starts on a Sunday and ends on a Saturday. For example, if you select a date range from Sunday, January 1 through Saturday, January 14, you have two data points for the two weeks. Each data point includes the sum for the week. Partial weeks are represented if your selected date range does not begin on a Sunday or end on a Saturday, but are not highlighted on the graph.
Graphs in your Google Analytics reports define a month by an actual calendar month, where the number of days can vary from 28 to 31, depending on the particular month. For example, if your date range includes the entire month of January, you would have one data point that is the summation of data from January 1 through January 31. Partial months are represented if your selected date range does not begin on the first day of the month or end on the last day of the month, but are not highlighted in the graph.