While creating a report, you will need to set the report date range which you can choose from various options in the report wizard, step #3:

You can choose from the frequently used date ranges on the left, or you can set a custom date.
Comparison Periods

Comparison periods help you understand the data more, by letting us compare the similar period data-wise. When entering a pre-defined date range, you would have two options to compare with.
Previous Period
Previous Year
The previous period compares the data with the previous period. Let's give an example!
For example, a 3-day week or 3-day month (in other words an unfinished week/month) will be compared to the first 3 days of the previous week or previous month. It will not be compared to the previous week/month in its entirety.
Just like this logic, the previous year lets us compare the data with its previous year's data.
If you have any questions about data ranges and/or comparison, simply reach us out at [email protected].