I would like to transfer a domain from one registrar to another. Could you tell me please how long the transfer procedure usually takes?

Depending on the two registrars and how fast you respond to confirmation emails it could take from one to three days.

Blue is correct, although it could take as long as 5 days if there is heavy activity at one of the registrars. It's best to start the process one full week before expiration. During the process there is typically no downtime since the nameservers remain are not changed during a transfer, unless your DNS is hosted by the registrar.

Think it depends on the company. Usually it takes a week.