Do you have a workbook as description is bit confusing or you can explain a bit more.
Unfortunately, due to confidentiality reasons, I cannot add any workbook. But let me add some more details.
The following calc, used in the title, counts the number of weeks shown in the report: MAX(DATEPART('week', [Date])) - MIN(DATEPART('week', [Date])) + 1
Up to the last week of 2018, when selecting 4 weeks, it counted 4, when selecting 8 weeks, it counted 8 etc. (see screenshots below):
Here comes the issue; when looking at a combination of weeks between 2018 and 2019, let's say the past 4 weeks, this same calc now counts 53 (weeks) when it should count 4 (weeks) (see screenshot in the original post). To be even more precise, the calc does 53-1+1 (max week - min week + 1) so this is why it returns 53 .