Fantastical permits you to add items to your calendar using plain English. This plugin permits you to do that using Alfred. See Fantastical;s usage guide for tips on what language to use for specifying tasks, specific calendars, or other settings. Usage is:

 fant Meeting with George at 3pm on Friday the 13th of May /work

Note: adding /work to the end would add the calendar item to the Work calendar. This is in Fantastical's Documentation. There are other tips and tricks to be found in their documentation.

This can be modified to work with Fantastical 1 by modifying the line in the AppleScript that says tell application "Fantastical 2" to be tell application "Fantastical".