Compare date read form file with input date - c

Question

i'm having serious problems with a project in C language. I've created a function that takes in input some data about an entry in a sport center, but now i've to modify this function so that this function:
asks in input the last name who's entering
by last name inserted, it must go to the file of registrations, search and read the last date of registration for that last name.
Once found, save this date somewhere and compare it with the expiration date of membership for the member with that last name. If the entry date is less or equal to the expiration date, must allow the inserting of data, otherwise, terminate the program with a message like this: "Your membership has expired".
My difficulties are in the point 2 and 3 of this request. Can someone please help me, i'm in serious trouble
I post the basic code on which i've to do this:
void add_entry()
Date_entry de;
Entry e;
Entry eTemp;
FILE *fEnt; //file corso
FILE *fInd; //file indice del corso
printf("Number: ");
scanf("%d", &e.number);
printf("Name: ");
scanf("%s", &e.name);
printf("Surname: ");
scanf("%s", &e.surname);
printf("Date (DD/MM/YYYY): ");
scanf("%d/%d/%d", &de.day3, &de.month3, &de.year3);
printf("Entry time(HH:MM): ");
scanf("%s", &e.entry_time);
printf("Exit time(HH:MM): ");
scanf("%s", &e.exit_time);
e.deleted = 0;
int cont = 0;
fEnt = fopen(EntryOpen,"r+b");
fread(&eTemp,sizeof(Entry),1,fEnt);
while(eTemp.deleted != 1)
{
fread(&eTemp,sizeof(Entrance),1,fEnt);
cont++;
}
int posInEntry = cont;
fseek(fEnt,cont * sizeof(Entrance),0);
fwrite(&e,sizeof(Entrance),1,fEnt);
fclose(fEnt);
Index x;
Index xTemp;
strcpy(x.key,e.surname);
x.value = e.number;
fInd = fopen(indexOpen,"r+b");
cont = 0;
fread(&xTemp,sizeof(Index),1,fInd);
while(strcmp(xTemp.key,"EMPTY") != 0)
{
fread(&xTemp,sizeof(Index),1,fInd);
cont++;
}
fseek(fInd,cont * sizeof(Index),0);
fwrite(&x,sizeof(Index),1,fInd);
fclose(fInd);
IndexCode y;
IndexCode yTemp;
y.kye = e.number;
y.value = posInEntry;
fInd = fopen(indexCodeOpen,"r+b");
cont = 0;
fread(&yTemp,sizeof(IndexCode),1,fInd);
while(yTemp.key != -1)
{
fread(&yTemp,sizeof(IndexCode),1,fInd);
cont++;
}
fseek(fInd,cont * sizeof(IndexCode),0);
fwrite(&y,sizeof(IndexCode),1,fInd);
fclose(fInd);
IndexCode ind[max];
fInd = fopen(indexCodeOpen,"rb");
int i;
for(i = 0; i < max; i++)
{
fread(&ind[i],sizeof(IndexCode),1,fInd);
}
fclose(fInd);
OrderIndexCode(ind,max);
fInd = fopen(indexCodeOpen,"wb");
for(i = 0; i < max; i++)
{
fwrite(&ind[i],sizeof(IndexCode),1,fInd);
}
fclose(fInd);
printf("Index Update completed.\n");