Unable to match Datetime type when trying to publish SQL CLR database

I am trying to find an old solution that posts a number of .net functions for a SQL Server database. But trying to post to a new database doesn't work on a function that manipulates dates.

Function that doesn't work:

[SqlFunction(TableDefinition="localtime datetime2", IsDeterministic=true, IsPrecise=true,
             DataAccess=DataAccessKind.None,
             SystemDataAccess=SystemDataAccessKind.None)]
public static DateTime ConvertFromUTC(DateTime utctime, string timezoneid)
{
    if (utctime.Kind == DateTimeKind.Unspecified)
        utctime = DateTime.SpecifyKind( utctime, DateTimeKind.Utc );

    utctime = utctime.ToUniversalTime();

    return TimeZoneInfo.ConvertTimeBySystemTimeZoneId( utctime, timezoneid );
}

      

        
        
        
      

    

The error message I get when trying to post is the following:

Creation of [dbo]. [ConvertFromUTC] ...

(268,1): SQL72014: .Net SqlClient Data Provider:

Msg 6551, Level 16, State 2, Procedure ConvertFromUTC, Line 1
CREATE FUNCTION for "ConvertFromUTC" failed because the T-SQL and CLR types for the return value do not match.

(268,0): SQL72045: Script runtime error

SQL generated from .net in an attempt to add a function:

CREATE FUNCTION [dbo].[ConvertFromUTC]
    (@utctime DATETIME, @timezoneid NVARCHAR (MAX))
RETURNS TABLE ([localtime] DATETIME2 (7) NULL)
AS EXTERNAL NAME [database].[IntelligentTutor.Database.Functions].[ConvertFromUTC]

      

        
        
        
      

    

The SQL definition for the version of the function in the existing database (which confirms that @MattJohnson was right about how it needs to be fixed):

CREATE FUNCTION [dbo].[ConvertFromUTC]
    (@utctime [datetime], @timezoneid [nvarchar](4000))
RETURNS [datetime] WITH EXECUTE AS CALLER
AS EXTERNAL NAME [database].[IntelligentTutor.Database.Functions].[ConvertFromUTC]