Remove array from Array List

I have a dropdown where you can select a date, the follow code is for the choiceLabels:

if(
    and(
        local!prefijo.prefijo = "listasis",
        a!isNotNullOrEmpty(local!prefijo.idTipoAsamblea_int),
        and(
            local!prefijo.idTipoAsamblea_int <> 2,
            local!prefijo.idTipoAsamblea_int <> 4,
            local!prefijo.idTipoAsamblea_int <> 6
            )
        ),
        union(
            text( index(local!fechaPorSerie , "fechaAsamblea", null ), "dd/MM/YYYY hh:mm a"),
            text( index(local!fechaPorSerie , "fechaAsamblea", null ), "dd/MM/YYYY hh:mm a"),
          ),
        union(
            text( local!fechasDeAsamblea, "dd/MM/YYYY hh:mm a" ),
            text( local!fechasDeAsamblea, "dd/MM/YYYY hh:mm a" ),
          )
)

If I have 18 dates, but 2 dates are the same... the array is goint to be 18.

But the array has a variable called idAsamblea, so every date has a different idAsamblea.

The follow code is for choiceValues:

if(
    and(
      local!prefijo.prefijo = "listasis",
      a!isNotNullOrEmpty(local!prefijo.idTipoAsamblea_int),
      and(
        local!prefijo.idTipoAsamblea_int <> 2,
        local!prefijo.idTipoAsamblea_int <> 4,
        local!prefijo.idTipoAsamblea_int <> 6
        )
    ),
    union(
          index(local!fechaPorSerie, "idAsamblea", null ),
          index(local!fechaPorSerie, "idAsamblea", null )
        ),
    union(
          indeX( local!Asamblea,  "idAsamblea", null ),
          indeX( local!Asamblea,  "idAsamblea", null ),
                                 
        )
    )

I want to remove the array duplicated and just leave one array with its date and idAsamblea.