Out of sequence

[codswallop]

I don't know what I have done but I have a whole page of thumbnails of my grandson in chronological order,but somehow I have just moved the last 30 to the top of the page.Is there any way that I can put this group to the bottom again. instead of doing them one at a time,which is very time consuming??? Thanks!!

[ACtheTROLL]

shift to detail view
click on the date column header (arrow points up)
shift back to thumbnail view