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Efficient way of representing Date

What is an efficient way of representing date?

Try the following code (Taken from Art of Computer Programming Vol 4)

var y = 2012; // Year 2012
var m = 6 // June
var d = 30 // 30th day on the calendar month

// Efficient representation (packing)
var result = (((y << 4) + m) << 5) + d;

Breaking this down further, we have

(y << 4)
Binary representation for 2012 is : 11111011100
Left shift by 4 : 111110111000000

Next we have,

((y << 4)+ m

111110111000000 + 110 (m = 6) = 111110111000110
Left shift 5, becomes 11111011100011000000

Next we add the days to it which bring us to the following equation

11111011100011000000 + 11110 = 11111011100011011110 ( Decimal : 1030366)

So our final result is : 1030366

// Unpacking
var day = result%32;

1030366 % 32 = 30 (once you have this, the rest is pretty straight forward)

var month = (result >> 5) %16;
var year = result >> 9;

Is there any other alternative for doing this? Maybe for other data types such as telephone.


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