When I open the gallery and sort by Time, there is always a section "Today", and it has several images I downloaded from the web...... months ago.
That's literally it. Why are old images showing under "Today"? There are other images I got from the web that are actually correctly sorted in older sections. But under "Today" I got around 20 web images that have been sitting there for months.
One thing I noticed is that this doesn't happen with photos taken with the phone. Such photos are always correctly sorted. So it's something with web images.
Android 5.0, Galaxy S5.