How t o get Google Now fetch info from Calendar?
Reminders set in the calendar will usually show up in google now. They do for my, I usually have a "notification" type reminder. Is the card enabled in Now?

Also, you can create actual reminders (with voice or text commands) that will create a Now notification. 
In the voice search, do "reminder: buy milk": you can then set the time period (evening/night/etc).

More info:
https://support.google.com/websearch/answer/3122344?hl=en