Converting a .NET Datetime to a DateTime2 in T-SQL

This article presents a handy T-Sql that extracts a DateTime value stored in .NET in a numerical field and converts it into a Sql Server DateTime (DateTime2 column). The T-SQL will convert into a DateTime2 with a SECOND precision. An assumption here is that any numerical value larger than 100000000000 contains a DateTime value. This is an acceptable assumption when you log data, as very large values usually indicate a datetime value. But you might want to have additional checking here of course in addition to what i show in the example T-SQL script. Here is the T-SQL that shows how we can convert the .NET DateTime into a SQL DateTime.

-- Last updated: March 18, 2025
-- Synopsis: This script retrieves detailed change log information from the ObjectChanges, PropertyChanges, and ChangeSets tables.
-- It filters the results based on specific identifiers stored in a table variable, in this example Guids. 

-- In this example T-Sql the library FrameLog is used to store a log

-- DateTime columns are retrieved by looking at number of ticks elapsed since DateTime.MinValue as 
-- DateTime columns are stored in SQL Server as a this numeric value. 


DECLARE @EXAMPLEGUIDS TABLE (ID NVARCHAR(36))

INSERT INTO @EXAMPLEGUIDS (Id)
VALUES
('1968126a-64c1-4d15-bf23-8cb8497dcaa9'), 
('3e11aad8-95df-4377-ad63-c2fec3d43034'),
('acbdd116-b6a5-4425-907b-f86cb55aeedd') --tip: define which form Guids to fetch the ChangeLog database tables which 'FrameLog' uses The form Guids can each be retrieved from url showing the form in MRS in the browser

SELECT 
o.Id as ObjectChanges_Id, 
o.ObjectReference as ObjectReference, 
o.TypeName as ObjectChanges_TypeName, 
c.Id as Changeset_Id, 
c.[Timestamp] as Changeset_Timestamp,
c.Author_UserName as Changeset_AuthorName,
p.[Id] as PropertyChanges_Id,
p.[PropertyName],
p.[Value],
p.[ValueAsInt],
CASE 
    WHEN p.Value IS NOT NULL 
         AND ISNUMERIC(p.[Value]) = 1 
         AND CAST(p.[Value] AS decimal) > 100000000000 
    THEN 
        DATEADD(SECOND, 
            CAST(CAST(p.[Value] AS decimal) / 10000000 AS BIGINT) % 60, 
            DATEADD(MINUTE, 
                CAST(CAST(p.[Value] AS decimal) / 10000000 / 60 AS BIGINT), 
                CAST('0001-01-01' AS datetime2)
            )
        )
    ELSE NULL
END AS ValueAsDate,
o.ChangeType as ObjectChanges_ChangeTypeIfSet
FROM propertychanges p
LEFT OUTER JOIN ObjectChanges o on o.Id = p.ObjectChange_Id
LEFT OUTER JOIN ChangeSets c on o.ChangeSet_Id = c.Id
WHERE ObjectChange_Id in (
 SELECT ObjectChanges.Id
  FROM PropertyChanges
  LEFT OUTER JOIN ObjectChanges on ObjectChanges.Id = PropertyChanges.ObjectChange_Id
  LEFT OUTER JOIN ChangeSets on ObjectChanges.ChangeSet_Id = ChangeSets.Id
  WHERE ObjectChange_Id in (SELECT Id FROM ObjectChanges where ObjectReference IN (
   SELECT Id FROM @EXAMPLEGUIDS
   ))) --find out the Changeset where ObjectChange_Id equals the Id of ObjectChanges where ObjectReference equals one of the identifiers in @EXAMPLEGUIDS
ORDER BY ObjectReference, Changeset_Id DESC, Changeset_Timestamp DESC

The T-Sql is handy in case you come across datetime columns from .NET that are saved as ticks in a column as numerical value and shows how we can do the conversion.