(AP Photo/Gus Ruelas)

Facebook's elusive algorithm, the one that makes some posts super visible and others seemingly invisible, is something most Facebook users might never understand. But behind most far-reaching posts is at least one subtle but important factor everyone can grasp: good timing.

It's hardly a revolutionary thought: Fewer people will see the picture you share of your new puppy if you post it in the middle of the night when most of your friends are asleep. It could do just fine, as far the number of likes, shares and comments go. But it will probably do much better if you are willing to wait until the optimal time to post it.

It turns out that time exists, according to a new study (pdf) conducted by Klout, a website that measures reach and influence on social media. As part of the the study, the researchers analyzed more than 25 million Facebook posts, as well as over 100 million reactions to them. What they found is that posting things at certain times of the day (late morning and early afternoons) and on certain days of the week (Tuesdays and Wednesday, most notable) tends to coerce more engagement from friends. The ideal time, however, does change slightly depending on where you live.

In New York, for instance, the ideal time to share things is just before noon. Thereafter, engagement falls consistently until it reaches its lowest point at about 3am. In San Francisco the optimal time to post things is a bit early (between 9am and 10am); in London, early afternoon is best; in Paris, there's a peak in the morning, and then again in the afternoon; and in Tokyo, early morning (between 7am and 9am) is ideal, but the fallout thereafter is much less severe. The Japanese, it seems, are happy to like, share, and comment on posts well into the night.

The chart below, plucked from Klout's study, shows how the probability that someone will react to any given post (likes, shares, or comments on it) changes throughout the day and week. San Francisco is the red line, New York city is the dotted green line, London the dotted blue one, Paris the dotted purple one, and Tokyo is the dotted aqua one. The peak probability of getting a like, share, or comment in response to a post is about the same in each city (the zero value for each line is marked by the straight line of the same color beneath it), so disregard the differences in height. Instead, notice how consistently engagement ebbs and flows throughout the week.

Facebook — city level reaction behavior

The trends, though they vary a bit by city, follow a similar pattern. On Tuesday and Wednesday, Facebook posts are the most likely to get reactions. On Thursday, friends are a bit shier with their likes, shares, and comments. On Friday, they are quieter still. And on the weekend they are the quietest. Monday, it seems, is something of an adjust period, when people are working their way back into both the week and their Facebook feeds.

Why the reaction to posting things at night tends to be more muted is both a result of something fairly obvious—fewer people are online—and something that's perhaps a bit less well-known. Most likes, shares, and comments come only a short time after someone posts something. A majority, in fact, "occur within the first 2 hours of posting times," the researchers note.

While that estimate includes Twitter, where the delay is even shorter on average (largely because people are more willing to scroll through older Facebook posts than older tweets that appear on their feed), it should be a pretty telling sign for anyone debating whether to share something before going to sleep or after waking up.

If you want as many people as possible to engage with your deep thoughts, clever quips, or hilarious memes, be patient, be calculated, and try to share them during the week, in the morning or early afternoon. Unless, of course, you live in Tokyo, where there is less of a work-life Facebook balance. In that case, maybe just don't post things when everyone else is asleep.