Sample code to get all the date properties on a given ItemType.

labs_GetDateProperties.cs

string itemTypeName = this.getType();

Item dateProps = inn.newItem("Property", "get");
dateProps.setProperty("data_type", "date");
dateProps.setAttribute("select", "name");
Item sourceIT = dateProps.createPropertyItem("source_id", "ItemType", "get");
sourceIT.setProperty("keyed_name", itemTypeName);
sourceIT.setAttribute("select", "id");
dateProps = dateProps.apply();

List<string> datePropNames = new List<string>();
for (int i = 0, numProps = dateProps.getItemCount(); i < numProps; i++)
{
    Item dateProp = dateProps.getItemByIndex(i);
    string datePropName = dateProp.getProperty("name", "");
    if (string.IsNullOrEmpty(datePropName))
    {
        return inn.newError($"Could not read name for property with ID: { dateProp.getID() }");
    }
    datePropNames.Add(dateProp.getProperty("name"));
}