For climbers traveling to Kalymnos by ferry from Piraeus (the port of Athens), the winter timetable of F/B Diagoras has been published. Kalymnos is connected to Piraeus three times a week.
From PIRAEUS to Kalymnos:
Tuesday at 15.00 (arrives Wednesday at 03.50)
Thursday at 15.00 (arrives Friday at 01.00)
Saturday at 19.00 (arrives Sunday at 06.10)
From KALYMNOS to Piraeus:
Monday at 23.10 (arrives Tuesday at 10.20)
Wednesday at 20.45 (arrives Thursday at 09.40)
Saturday at 03.10 (arrives Saturday at 13.10)
This timetable is valid through January 7, 2013. It is also available here: http://www.bluestarferries.com/site/content.asp?sel=624&loc=2