creation of header files in c++

Here is my code for a small application to create header file and use it..but i am getting some error can any one suggest me what to do

time.h
.................

#include<stdio.h>
#include<math.h>
void main()
{

void secondstominutes();
void minutestohours();
void hourstodays();

}
void secondstominutes()
{
int value;
float min;
printf("\n give the value");
scanf("%d",&value);
min= (float)(value)/60;
min=ceil(min);
printf("\n%d min",min);
}
void minutestohours()
{
int value;
float hours;
printf("\n give the value");
scanf("%d",&value);
hours = (float)(hours)/60;
hours = ceil(hours);
printf("\n%d hours",hours);
}
void hourstodays()
{
int value;
float days;
printf("\n give the value");
scanf("%d",&value);
days=(float)(value)/24;
days=ceil(days);
printf("\n%d days",days);

}




....................
time.c
..........

#include<stdio.h>
 #include"time.h"
{
int choice, value;
printf("\n give choice\n 1. Convert seconds into minutes\n 2. Convert minutes into hours\n 3. Convert hours into days");
scanf("%d",&choice);
      if(choice==1)
      {

      secondstominutes();

      }
      else if(choice==2)
      {

      minutetohours();
      }
      else if(choice==3)
      {

      hourstodays();
      }
}