For a report, when defining the date parameters, you have the ability to define a report within a moving window.
Example: Last Week would give a report that always shows the last week. (Monday to Sunday)
Last Month would give a report that always shows the last month. (From the 1st of the month to the last day e.g. 28th, 29th, 30th, 31st)
When a new graph or report is created, the default date range is This Season.
When This Season is clicked, other date range options appear. Hovering over This Season will describe what this This Season means in terms of a date range. This season runs the same as two calendar years, Jan 1, 2015 to Dec 31, 2016.
For this example let's change the date range to Last 2 Weeks and click the fixed date icon .
Next you will notice the date range selection no longer states Last 2 Weeks, it changed to Feb 22, 2016 - Mar 6, 2016. This indicates that the Fixed Date status is turned on.
Going forward, while the Fixed Date status is on, this report will always show the relevant metrics for the last two weeks from the current date.
For example: Today is Tuesday March 8, 2016. The last two weeks are Monday, February 22, 2016 to Sunday, March 6th, 2016.
If we run the same report next Tuesday, March 15th, the date range shown will be Monday, February 29th to Sunday March 13th.