Long time ago, scientist observed that, at each whole night, twelve groups of stars passes in the sky from north east to south west.
They were really surprised... but they thought, what happened in the sky at day time ?
It was very hard to observe the movement of stars in the sky at day time, but at last, they find the way and once the opportunity comes for the scientist in a total solar eclipse time ! They found, groups of stars passes through the same way at day time also and after deep observation and examining the movement of those groups of stars, scientist assumed, number of those passing groups of stars at day time is as same as at night ! They think, its a miracle...!!
That observation opened a new idea of hours in a day ! From that time, day and night divided into two part equally into twelve hours !!