8/16/2015   6:30:00 PM     8:00:00 PM    1.50   Floorplan
8/19/2015   10:00:00 AM    10:30:00 AM   0.50   Layout
8/19/2015   12:00:00 PM    3:30:00 PM    3.50   staircase

8/16/2015   1.50    Floorplan
    8/19/2015   4.00    Layout, staircase

=QUERY(A2:E4, "select A, sum(D) group by A")

=JOIN(", ", TRANSPOSE(UNIQUE((QUERY(A2:F4, "select E where day(B) = day(A6)))))

=JOIN(", ", UNIQUE(QUERY(A2:F4, "select E where day(A) ="&day(A6))))

=join(", ", unique(filter(E$2:E$4, A$2:A$4 = A6)))