Function dateToMjd( year, month, day )

Description:
Converts a calendar date 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)
Return Value (floating point):
modified Julian date corresponding to 00:00:00 of the date specified by the arguments
Example:
dateToMjd(1999, 12, 31) = 51543.0
Signature:
double dateToMjd(int, int, int)