Function dateToMjd( year, month, day, hour, min, sec )

Description:
Converts a calendar date and time to Modified Julian Date.
Parameters:
year (integer)
year AD
month (integer)
index of month; January is 1, December is 12
day (integer)
day of month (the first day is 1)
hour (integer)
hour (0-23)
min (integer)
minute (0-59)
sec (floating point)
second (0<=sec<60)
Return Value (floating point):
modified Julian date corresponding to arguments
Example:
dateToMjd(1999, 12, 31, 23, 59, 59.) = 51543.99998
Signature:
double dateToMjd(int, int, int, int, int, double)