It is the case with all social/new media tools – you want to get the most bang for your efforts and get the most eyes reading your content. That way, someone's going to share it and ultimately someone's going to talk about it.
But how do you know when is the best time to post that link, comment, or story?
Specifically referring to Google+ for this post, there is a tool called Google+ Timing which does exactly that; gives a great breakdown and analysis of what time throughout the day, depending on your timezone location, when you should be posting content on Google+
As you can see for me, I need to focus the majority of my posting efforts on Thursday mornings between 8-9am.
Obviously all metrics and analytical tools should be taken with a grain of salt if the algorithm isn't known, but it's still nice to have a report showing when you could possibly make the most optimum impact with your efforts.
If you're on Google+ you can access the Google+ Timing tool here.