These tables are for use with the Current Atlas: Juan de Fuca Strait to Strait of Georgia (published by the Canadian Hydrographic Service), and make it easier to use by providing pre-computed tables of chart numbers for any given date and time. Oh, and they're free for non-commercial use!
Current Atlas Tables: Juan de Fuca Strait to Strait of Georgia
http://borsboom.io/current-atlas-tables/