This is a great article i found while thinking about when the best time to publish my blog posts would be to get the most viewers. Basically it is common sense, but there are some nuggets of wisdom in the snippet below. If you would like to read the full article go to the ezine article directly
When is the best time to post your status update?
Well there are many factors you need to take into account as there is no one particular set time that necessarily yield the best results.
Is the update time critical? - By this I mean, are you updating your own status about something you're doing right now? If so, then the most effective time to post is either before or during the event. People are more likely to comment on a status about something that you're about to do rather than something you've previously done. Posting later on also runs the risk of someone different posting about it previously and stealing your thunder (e.g. viewing a sporting event).
If the status is not really time critical (e.g. you happen to be posting a joke or some sort of intriguing remark) then the best moment I have found to post status updates is weekday evenings. The most amount of individuals I have witnessed on Facebook (looking at exactly who is on-line through Facebook chat) has been Monday to Thursday evening.
The reason for this I believe to be twofold. First of all, numerous people log on often when they are about to finish or have just finished work. This means generally there is typically a spate of activity between roughly 5 or 6pm. I post quite a few of my status' at 5pm as that's when I normally finish work and log on. Several other people do the same thing and will therefore view your status near the top of their own news feed.
Secondly, individuals usually tend to go out much less on weekday evenings in comparison to weekends, consequently far more people are usually on-line for this reason when they're returning home after work, usually somewhere between 7 and 9pm approximately.
One more very good time to post, is weekday lunchtime (between 12 and 2pm). This will mean your status is shown to people who are looking at Facebook from work at lunchtime as well as college students who are just getting up (probably with a rather tender head! ).
When is not a good time?
Weekends aren't a good time to post status updates that you would like to be popular for a couple of reasons. For starters, most people have a tendency to go out more at the weekends and will therefore use Facebook less, therefore fewer people will see your status update. Furthermore, even the people who do log on often will not want people to know they're on-line at the weekend because it will imply that they are not social and staying in at the weekend while they should be out and about having fun. As a result they will not socialise with anyone during these times on Facebook so that it looks like they're not on-line and potentially out and about.