Do not rely on the System class Java calendar, Skull Halo.

Package test2;
Import Java.util.Scanner;
public class Demo {
public static void Main (String args[]) {
Scanner input=new Scanner (system.in);
Boolean in1=false;
Boolean in2=false;
int year;
int month;
int year_day=0;
int month_day=0;
int day_count;
int week;//days a week
int month_days=0;
int space=0;
int C;
int ln=1;//A counter that starts wrapping as the second line of output
do{
System.out.println ("Please enter Year:");
Year=input.nextint ();
if (year<0) {
SYSTEM.OUT.PRINTLN ("Year input error, please re-enter");
In1=true;
}else{in1=false;}
}while (in1);
do{
System.out.println ("Please enter the month:");
Month=input.nextint ();
if (month>12| | month<1) {
SYSTEM.OUT.PRINTLN ("Month input error, please re-enter");
In2=true;
}else{in2=false;}
}while (in2);
The/*for Loop calculates the number of days between the year_day of 1900 and the year in which it was entered.
for (int a=1900,day;a<year;a++) {
if ((a%4==0&a%100!=0) |a%400==0) {
day=366;
}else{day=365;}
Year_day=year_day+day;
}
/*for cyclic computation of the first month_day, that is, the number of days before the year January to the entered month (month) * *
for (int b=1;b<month;b++) {
Switch (b) {
Case 1:case 3:case 5:case 7:case 8:case 10:case 12:
month_day=month_day+31;
Break
Case 4:case 6:case 9:case 11:
month_day=month_day+30;
Break
Case 2:
if ((year%4==0&year%100!=0) |year%400==0) {
month_day=month_day+28;
}