How to count the number of days of the taken back up database is old using C#

Yes.

sql Server 2005 database
Code for Back Up-
public static void BackupDB(string backupDestinationFilePath)
{
try
{
// Console.WriteLine("Backup operation started");
Backup backup = new Backup();
//Set type of backup to be performed to database
backup.Action = BackupActionType.Database;
backup.BackupSetDescription = "BackupDataBase description";
//Set the name used to identify a particular backup set.
backup.BackupSetName = "Backup";
//specify the name of the database to back up
backup.Database = "DB_Jaggry";
//Set up the backup device to use filesystem.
BackupDeviceItem deviceItem = new BackupDeviceItem(
backupDestinationFilePath,
DeviceType.File);
backup.Devices.Add(deviceItem);

// Setup a new connection to the data server
ServerConnection connection = new ServerConnection();
Server sqlServer = new Server(@"SNEHA-PC\SQLEXPRESS");
//Initialize devices associated with a backup operation.
backup.Initialize = true;
backup.Checksum = true;
backup.ContinueAfterError = true;
backup.LogTruncation = BackupTruncateLogType.Truncate;
backup.SqlBackup(sqlServer);
MessageBox.Show("Backup operation succeeded");
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}