filename=2008-11-10-myfilename
newfilename=${filename##*-}
echo $newfilename

echo $filename | \
 sed  's/\(^[1-2][0-9]\{3\}\)-\([0-1][0-9]\)-\([0-3][0-9]\)-\([A-Z_0-9a-z]*\)/\4/'  | read newfilename
if [[ ! -z newfilename ]] ; then
   filename=$newfilename
fi

/* chpdt.c 
usage chpdt filename 
      echo "$filname" | chpdt
*/
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <stdio.h>
#define isleapyr(y) (((y) % 4) == 0 && ((y) % 100) != 0 || ((y) % 400) == 0)
int leap[12]= {31,29,31,30,31,30,31,31,30,31,30,31};
int nleap[12]={31,28,31,30,31,30,31,31,30,31,30,31};


char  *date_ok(char *result, char *src)
{
	int value=atoi(src);
	int month=0;
	char *p=src;
	int *v=nleap;

    if( value >= 1900 && value < 2038 && (p=strchr(p, '-')) != NULL )
    {
        if(isleapyr(value))        
        	v=leap;
		value=atoi(++p);
		if(value >= 1 && value < 13 && (p=strchr(p, '-')) != NULL)
		{
			month=value;
			value=atoi(++p);
			if( value > 0 && value < v[ month - 1 ] )
				if( (p=strchr(p, '-')) != NULL)
					result=++p;
		}
    }
    return result;
}

char  *name_ok(char *p, char *src)
{
	if(src[4]=='-' && src[7]=='-' && src[10]=='-')
		p=date_ok(p, src);
	return p;
}

int main(int argc, char **argv)
{
	int retval=0;
	char tmp[PATH_MAX + 2]={0x0};
	char *p=NULL;
	if (argc < 2)
	{
		if(fgets(tmp, sizeof(tmp), stdin) ==NULL)
		{
			perror("I/O error");
			retval=1;
		};
		p=strchr(tmp, '\n');
		if(p!=NULL)
			*p=0x0;
	}
	else
		(void)strncpy(tmp, argv[1], PATH_MAX);
	p=tmp;
	if(strlen(tmp) > 10 && !retval) /* will return zero length if string is "date-"*/
		p=name_ok(p, tmp);
    if( fprintf(stdout, "%s", p) < 0)
    {
    	perror("I/O error");
    	retval=1;	
    }
    return retval;
}