If you have selected a day/period in one view, then switch to another less detailed view and click on the period with the already selected day/period, the selection will only include the period before/after the selected day/period (depending on which side of the selection you click on).
In day view (D), you select the first three days of year 2018, then move to year view (Y) and click on 2018. Only 362 days will be selected (from 4th of January through 31st of December). This is really hard to spot as it looks like the whole year has been selected.
I am not sure if this is a bug or a feature, but when I open year view and click on 2018, I would expect the whole year to be selected regardless of what my selection in a previous view was. This has already caused some misunderstandings in my project.