read and change time in .srt file

[camder23]

can anyone help me to change the time in .srt file
wat i support to is increase subtitle time in 3 seconds(i.e the subtitle will after actors speaks 3 seconds)
wat i have so far:

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include "Subtitle.h"
typedef char string[16];
struct subStruct{
int order;
long statHour;
long statMin;
long statSec;
long endHour;
long endMin;
long endSec;
string sub;
};

/*
* Check all values in the array
* intput : array of characters
* output : No Change
* return :
* TRUE if array contains only [a..z A..Z 0..9]
FALSE if vise versa
*/
int check_value(char * value){
int i;
int len = strlen(value);//lenght of the string
for(i = 0; i<len;i++){
if(isalnum(*(value + i))==FALSE)
return FALSE;
}

}
int check_param(char *i_option,char *i_value,char *d_option,char *d_value,char *t_option,char *t_value,char *o_option, char *o_value){
int param_num;
if(param_num >= 7){
//check option
if(strcmp(i_option,"-f") != 0) return FALSE;
if(strcmp(d_option,"-d") != 0) return FALSE;
if((strcmp(d_value,"-u") && strcmp(d_value,"-d")) != 0) return FALSE;
if(strcmp(t_option,"-t") != 0) return FALSE;
if(strcmp(o_option,"-o") != 0) return FALSE;

if(check_value(i_value)==FALSE);
if(check_value(d_value)==FALSE);
if(check_value(t_value)==FALSE);
if(check_value(o_value)==FALSE);
} else {
return FALSE;
}
return TRUE;
}
long HourconvertMil( long hour){
return (hour * 3600000);
}
long MinconvertMil( long min){
return (min * 60000);
}

long SecconvertMil( long sec){
return (sec * 1000);
}
void convertStruct(char *fileName,struct subStruct * sub){
FILE *textFile;

int count = 0;
char buff[500];
char *ptr;
textFile = fopen(fileName,"r"); /* open text file for reading */

if (textFile == NULL){
perror("File can't be found");
return;
}
sub = (struct subStruct*) malloc(sizeof(struct subStruct));
while(!feof(textFile)){
fgets(buff, 255, textFile);
(*sub).order = ptr[0]; /*subttile order */
printf("\n");
if(ptr ==':'){
ptr = strtok(0, ":");
(*sub).statHour = ptr[0];
ptr = strtok(0, ":");
(*sub).statMin = ptr[0];
ptr = strtok(0, ":");
(*sub).statSec = ptr[0];
ptr = strtok(0, ":");
(*sub).endHour = ptr[0];
ptr = strtok(0, ":");
(*sub).endMin = ptr[0];
ptr = strtok(0, ":");
(*sub).endSec = ptr[0];
}
printf("\n");
strcpy((*sub).sub, ptr);
}
fclose(textFile);

}
long converMil(long hour,long min, long sec){
return (hour*3600000)+(min*60000)+(sec*1000);
}
long mil2hour(long mil){
long hour;
hour=(mil/(1000*60*60));
return hour;
}
long mil2min(long mil){
long min;
min=(mil%(1000*60*60))/(1000*60);
return min;
}

long mil2sec(long mil){
long sec;
sec=(((mil%(1000*60*60))%(1000*60))/1000);
return sec;
}
void changeTime(long time,char * srtFile){
FILE * f1;
long stime;
long etime;
struct subStruct * sub;
f1 = fopen(srtFile,"wa");
(*sub).order;
stime=((converMil((*sub).statHour,(*sub).statMin,(*sub).statSec)) +time);
// etime=((converMil((*sub).endHour,(*sub).endMin,(*sub).endSec) +time));
(*sub).statHour = mil2hour(stime);
(*sub).statMin = mil2min(stime);
(*sub).statSec = mil2sec(stime);
(*sub).endHour = mil2hour(etime);
(*sub).endMin = mil2min(etime);
(*sub).endSec = mil2sec(etime);
(*sub).sub;
fwrite((struct subStruct*)sub,sizeof(struct subStruct),1,f1);
fclose(f1);
}

wat i am doing now is:
i store structure into the .srt file then
i read the .srt file to get the times then change into millisecond
after that, i add the 3000millsecond with the time that i just change into millisecond
then, i changed back the time format hour:min:second, millisecond
then save the changed time into the original .srt file

my problem is when i try to save the changed times into the original .srt file
the format is changed.
can any1 help me to fix the problem.
thanks for your time