There appears to be a problem with the mktime() and difftime() functions when the time rolls over the end of a month...
Here's the code that exhibits the problem...
// CITY PARKING
#include <stdio.h>
#include <time.h>
// monetary values
#define PRICE_CAR 1.25 // car rate per hour
#define PRICE_TRUCK 2.50 // truck rate per hour
#define GATE_CHARGE 5.00 // flat rate for entry
#define GATE_TIME 30 // flat rate period
#define SALES_TAX 17.5 // tax addon in percent
int _cdecl main( void )
{ int tOnLot = 0;
float Rate = PRICE_CAR;
printf("\n\t\t ***** CITY PARKING *****\n\n");
// get time in and time out
{ struct tm tIn = {0}, tOut = {0};
printf("Enter times as\tYYYY MM DD HH MM\n");
printf("Time In :\t");
scanf("%d %d %d %d %d",&tIn.tm_year,&tIn.tm_mon,&tIn.tm_mday,
&tIn.tm_hour,&tIn.tm_min);
printf("Time Out :\t");
scanf("%d %d %d %d %d",&tOut.tm_year,&tOut.tm_mon,&tOut.tm_mday,
&tOut.tm_hour,&tOut.tm_min);
tOnLot = difftime(mktime(&tOut),mktime(&tIn)) / 60; } // time in minutes
// get vehicle type and set hourly rate
{ getchar();
printf("\nIs this a Truck? (Y or N) : ");
int vt = getchar();
if ( vt == 'y' || vt == 'Y')
Rate = PRICE_TRUCK; }
// display time
printf("\nTime on Lot : %d minutes\n\n",tOnLot);
// calculate billable time
{ float Total = 0;
float Time = 0;
float Tax = 0;
tOnLot -= GATE_TIME;
printf("Gate Fee :\t%8.2f\n",GATE_CHARGE);
if( tOnLot > 0)
{ Time = (tOnLot * Rate) / 60.0;
printf("Time :\t%8.2f (%dmin @ $%.2fhr) \n",Time,tOnLot,Rate); }
Total = GATE_CHARGE + Time;
printf("SubTotal :\t%8.2f\n", Total);
Tax = Total * (SALES_TAX / 100.0);
printf("Sales Tax :\t%8.2f\n\n",Tax);
Total += Tax;
printf("Total Due :\t%8.2f\n\n",Total); }
return 0; }
I'm attaching an image that shows the problem... note that in all cases the "time on lot" should be 10 minutes.
