How to archiv part of the table information based on the timestamp?

In my database I want to archive some rows based on the time stamp. I read that horizontal partitioning will do that. This partitioning will insert the rows from the table into some other Database - Tablename. In retrivng those rows back I need to issue separate queries and UNION the result set. Is this way is correct or there any better ways to do this? If it is I have another question. If I add a new column to the table I partitioned, what will happen to the table that I stored in other Database. Is that going to add this new column too?

If possible please give me a sample code or queries to partition the database.

Thank you.

we run a archive job daily (we keep only 1 year data). the statement looks something like below

insert into archive_table select * from source_table where convert(varchar(12),timestampval,112) <= convert(varchar(12),(getdate()-365),112)
delete from source_table where convert(timestampval <= convert(varchar(12),(getdate()-365),112)


If we add a column in source_table, we also add a column in the archive_table.