This is not a really Bug because the convention date per month is 30 and Stat based its range on this value.
In Stat 5.8 Stat gives you an additional option to choose the range date from where to extract data. In this sense, it has been fixed as implemented feature.
I compared Statistic report and Migration report by date on both versions 5.7.4 and 5.8.0.
If you are talking about the date to select from the list option 'past 30 days', 'past 90 days', and so on,
then in 5.8.0 you will have an additional option 'Specific date range' where you have to select the days 'from' - 'to' date then this has been solved.