Health scientists are becoming more and more interested in the citrulline content of watermelon. Citrulline is an amino acid that is commonly converted by our kidneys and other organ systems into arginine (another amino acid). The flesh of a watermelon contains about 250 millligrams of citrulline per cup.
The Julian day or Julian day number (JDN) is the number of days that have passed since the initial epoch defined as noon Universal Time (UT) Monday, January 1, 4713 BC in the Julian calendar. That noon-to-noon day is counted as Julian day 0. Thus the multiples of 7 are Mondays.
I cannot tell you why they do that, you would have to ask them. A julian date is the number of days from a fixed point in time. 1* select to_char( sysdate, 'j' ), to_char( to_date( 1, 'j' ), 'dd-mon-yyyy. AD' ) from dual. ops$tkyte@8.0> /.