Kim Peek, the inspiration for the film Rain Man, had an amazing ability to memorise information. One of his ‘tricks’ was to ask for any date and he would instantly tell you the day of the week it fell upon. You can learn to do this too, albeit slightly slower, at first at least.

 

 

Prepare yourself though it’s not going to be easy, it entails not only a few mental arithmetic back-flips but being able to recall the following number – month date system.

 

January*, October	0
May	1
August	2
February*, March, November	3
June	4
September, December	5
April, July	6
*reduce by 1 on a leap year	x

 

Alternatively you could memorize the number 033614625035 which is the months in order. You must remember to subtract 1 to January and February if the year is a leap year (if the year is divisible by 4 and is not the turn of a century unless it’s also the turn of a millennium [ie for 1900 you wouldn't have to adjust but in 2000 and 1948 you would]).

 

Right so lets get down to the actual calculation, take the last two digits of the year then add a quarter of itself (whole numbers only). Then for dates prior to 2000 add 1 then add an additional 2 for each 100 years before that or subtract 2 for every hundred years past 2000. Next we  add the month code from above. Then add the day of the month. Lastly we divide by 7, we actually just want the remainder from dividing by 7 some may know this as the modulus.

This then gives us the day of the week starting with Sunday = 1, Monday = 2 and so on, ending with Saturday = 0.

 

Example

25th December 1988

Last two digits of the year: 88

+1/4 of it’s self: 110

+1 for being before 2000: 111

+5 for being December: 116

+25 for the day of the month: 141

remainder from dividing by 7: 1

Christmas day 1988 was a Sunday

 

Tip: since we are eventually taking the remainder from dividing by 7 you can work round this number as soon as you do the second step of adding a quarter of the date onto its self. (eg as above 88 + 22 = 110 simplifies to 5 + 1 for the century = 6 + 5 for the month = 11 simplifies to 4 + 25 for the day = 29 simplifies to 1 = Sunday.)

 

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Sick of those annoying facebook groups that make you click “like” (as its now called) in order just to see the content that you are meant to be liking? I know I am.

With this is mind I decided to find out how they work and how to get the content without announcing to all my friends that “Tom Hodson likes The Top 10 Curtain Designs of 2010″ or something equally as exciting.

After a little research trawling facebook and checking out the page source to these groups I discovered that the ‘user only’ content in these groups (or at least all the ones I found) rests inside a html element called a span.

These spans have their visibility set to hidden for non-members of the group or page. This means the content is sitting there in your browser but it’s just not being shown.

Once we know this its trivial to knock up a bit of javascript that goes through all the spans on the page setting their visibility to visible. This looks something like this:
JavaScript:var spans = document.getElementsByTagName('span'); for (i = 0; i < spans.length; i++) {spans[i].style.visibility = 'visible';}; void 0

You can either paste that into the browser’s address bar every time you want to use it or drag this link (FBUnhide) into your bookmark bar to make a nice button.

You found the hidden message! Hurrah!

Update 9/5/2010: Now available as a firefox extension. NoLikey

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