are databases in same server? if yes, you can simply use INSERT...SELECT to insert required data from main table to your backup table. Then you may purge it from main table if you want. it will be like
INSERT INTO DB2.dbo.BackupTable
SELECT column1,column2,...
FROM DB1.dbo.MainTable
WHERE datefield >=@StartDate
AND datefield< @EndDate +1
also see here
http://visakhm.blogspot.in/2012/12/different-ways-to-implement-date-range.html
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SQL Server MVP
http://visakhm.blogspot.com/