SocialFresh complied some great insights about when is the best time to post your Facebook page.

Age stereotypes are key when thinking about your target audience. Younger users are more prone to talk about themselves and think about themselves, whereas older users are more prone to think of others.

• Use this to your advantage when launching a contest, viral campaigns, or Facebook marketing (PPC) ads.
• Posts are most effective at 11:00AM, 3:00 PM, and 8:00 PM. Post during these times to grab the attention of the largest slice of your target market.
  *However, be sure to respond to your fans whenever they are active, no matter what time of day.
  
• Test and find your own sweet spots, every community is different
• Post during the week for better conversations, relationship building and engagement of your brand. This would also be true of launching contests, polls, viral campaigns, etc.

Via: SocialFresh