How to show additional column for Dynamic list

I have two fields: StartDate and EndDate and I want a Period presentation for them. I know I could create additional attribute and store presentation data there, but I really want to compose presentation during list showing. How could I do this? I know that for DataComposition Scheme I could define function for the field inside the query. Could I do the same or something like this for ListForm?

You can use a custom query in the DynamicList (mark the CustomQuery property for that) and provide a custom field using query language, for example:

SELECT
   CatalogContracts.Ref,
   CatalogContracts.StartDate,
   CatalogContracts.EndDate,
   DATEDIFF(CatalogContracts.StartDate, CatalogContracts.EndDate, MONTH) AS Period
FROM
   Catalog.Contracts AS CatalogContracts

Why none of this works?

YEAR(Document.Date) + " year"

CAST(YEAR(Document.Date) AS Number(4,0)) + " year"

CAST(CAST(YEAR(Document.Date) AS Number(4,0)) AS String)

It is not possible to cast a number to a string in query.

Please explain your task more directly. Provide a template of what you would like to implement.

I suggest you the following technique:

• Add a column group with your start date and end date fields
  
• Set Group property of the column group to In cell
  
• Mark Show in header check box for the group
  
• Set Title for the group as Period
  
• Formatted your fields as you like using Format property of those fields
  
• Unmark Show in header check boxes for start date and end date fields
  
• You can add a separator using another field in the Query with " - " between them