Thanks to other posts on Community this code works! Might not be the most efficient but it works!
var fs = FeatureSetByPortalItem(Portal('https://www.arcgis.com'), 'xxxxx', 0, ["AKDate"], false);
var track_dt = Distinct(fs,["AKDate"]);
var fs2 = FeatureSetByPortalItem(Portal('https://www.arcgis.com'), 'xxxxxx', 2, ["AKDate"], false);
var spawn_dt = Distinct(fs2, ["AKDate"]);
var fs3 = FeatureSetByPortalItem(Portal('https://www.arcgis.com'), 'xxxxxx', 1, ["AKDate"], false);
var pred_dt = Distinct(fs3, ["AKDate"]);
//return track_dt
var fs4 = FeatureSetByPortalItem(Portal('https://www.arcgis.com'), 'xxxxx', 0, ["AKDate"], false);
var hschool_dt = Distinct(fs4, ["AKDate"]);
var Dict = {
'fields':[
{'name': 'AKDate', 'type': 'esriFieldTypeString'}
],
'geometryType': '',
'features':[]
};
var i = 0;
for (var f in track_dt){
Dict.features[i] = {
'attributes':{
'AKDate': f['AKDate'],
}
};
i++;
}
for (var f in spawn_dt){
Dict.features[i] = {
'attributes':{
'AKDate': f['AKDate'],
}
};
i++;
}
for (var f in pred_dt){
Dict.features[i] = {
'attributes':{
'AKDate': f['AKDate'],
}
};
i++;
}
for (var f in hschool_dt){
Dict.features[i] = {
'attributes':{
'AKDate': f['AKDate'],
}
};
i++;
}
Console(Text(Dict))
var s_dt = FeatureSet(Text(Dict));
return Distinct(s_dt,['AKDate']);