I have downloaded some glacier outlines from the GLIMS database (http://www.glims.org/maps/glims) as a SHP file.
This contains multi-temporal data, that is, more than one outline per glacier (more info on https://www.glims.org/Workshops/2017_vienna/glims_rgi_update_at_egu2017_splinter_meeting.pdf); outlines are grouped by glacier.
How can I extract a "snapshot" of a particular time (especially the most recent version in each outline group, knowing that different groups have different timestamps), if possible in QGIS? It is done in the presentation I have linked above, but with no explanation.
Sample data uploaded here (file glims_polygons): https://ufile.io/rvotq