question: public static double calculateJulianDay ( Date date ) { Calendar cal = Calendar . getInstance ( TimeZone . getTimeZone ( "GMT" ) ) ; cal . setTime ( date ) ; double hour = cal . get ( Calendar . HOUR_OF_DAY ) + cal . get ( Calendar . MINUTE ) / 60.0f + cal . get ( Calendar . SECOND ) / 3600.0f ; int year = cal . get ( Calendar . YEAR ) ; int month = cal . get ( Calendar . MONTH ) + 1 ; int day = cal . get ( Calendar . DAY_OF_MONTH ) ; double jd = 367.0 * year - Math . floor ( 7.0 * ( year + Math . floor ( ( month + 9.0 ) / 12.0 ) ) / 4.0 ) + Math . floor ( 275.0 * month / 9.0 ) + day + 1721013.5 + hour / 24.0 ; return jd ; }
target:  Calculate the Julian Day for a given date using the following formula: JD = 367 * Y - INT(7 * (Y + INT((M + 9)/12))/4) + INT(275 * M / 9) + D + 1721013.5 + UT/24 Note that this is only valid for the year range 1900 - 2099.