Please see the attached screenshots,

• select "1m" and move slider to oldest position, oldest event is "29 Jan 2015 23:32:07":
  

• select "All" and move to oldest page:
  

• oldest event is "29 Jan 2015 23:32:34":
  

• selecting "All" again shows "29 Jan 2015 23:32:07":
  

It seems that paging doesn't calculate stime or period correctly.