Binary Coded Decimal (BCD):

This type of binary clock has six columns, each column representing a single decimal digit. The first two columns the hours, middle two columns the minutes and last two columns the seconds.

The bottom row in each column represents 1 (or 2⁰), with each following row above that representing higher powers of two, up to 2³ (or 8).

To calculate the time; add the values in each column that the illuminated lights represent, then read these from left to right. (see table below)

          Hours     Minutes     Seconds
         -------    -------     -------
     8 |   0  0       0  1       0  0
     4 |   0  0       1  0       1  1
     2 |   1  0       0  0       0  1
     1 |   0  1       1  1       0  0
         ==============================
decimal:   2  1    :  5  9    :  4  6

True Binary:

A true binary clock works on the same principal as a BCD clock except there are only three columns, one each representing hours, minutes and seconds. The rows on a true binary clock go up to 2⁵ (or 32). The time is calculated exactly the same as before, with the user adding the value for each column then reading left to right. (see below)

          Hours    Minutes    Seconds
         -------   -------    -------
    32 |    0         1          1
    16 |    1         1          0
     8 |    0         1          1
     4 |    1         0          1
     2 |    0         1          1
     1 |    1         1          0
         ============================
decimal:   21    :   59    :    46