How to add date to SQL database backup name?

Question

SQL Server

Hey!
With this method:

DECLARE @filename varchar(255) 
SET @filename = 'D:\Backup\DB_hourly_' + REPLACE(convert(char(19),GetDate(),120),':','-') + '.bak' 
BACKUP DATABASE [db] TO [email protected] WITH RETAINDAYS = 7, NOFORMAT, INIT, NAME = N'db-Full Database Backup', SKIP, NOREWIND, NOUNLOAD,  STATS = 10

only the date is added to the file name, although the time should be, but it is not. What is the problem here?