let
a = [datetime],
list1 = Table.SelectRows([table], each [start] <= a)[Index],
list2 = Table.SelectRows([table], each [end] >= a)[Index],
result = List.Intersect({list1, list2})
in if List.IsEmpty(result) then null else result{0}
CALCULATE(<expression>[, <filter1> [, <filter2> [, …]]])
CALCULATE(FIRSTNONBLANK(table[date],""), table[year]=YEAR(NOW()))