diff --git a/legacy/app/common/util_date.c b/legacy/app/common/util_date.c
index 70cbed6..04aa43f 100644
--- a/legacy/app/common/util_date.c
+++ b/legacy/app/common/util_date.c
@@ -1,135 +1,52 @@
-/*
- * util_date.c - 일자/영업일 유틸리티 (plain C)
- */
-#include "acq_util.h"
-
-#include <string.h>
-#include <ctype.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <time.h>
 
-static int is_all_digit(const char *s, int len)
-{
-    int i;
-    for (i = 0; i < len; i++) {
-        if (!isdigit((unsigned char)s[i]))
-            return 0;
-    }
-    return 1;
+#define DATE_BUF_SIZE 32
+
+typedef struct {
+    int year;
+    int month;
+    int day;
+} date_t;
+
+int date_parse(const char* str, date_t* out) {
+    if (!str || !out) return -1;
+    return sscanf(str, "%4d-%2d-%2d", &out->year, &out->month, &out->day);
 }
 
-static int to_int(const char *s, int len)
-{
-    int i, v = 0;
-    for (i = 0; i < len; i++)
-        v = v * 10 + (s[i] - '0');
-    return v;
+int date_format(const date_t* d, char* buf, size_t len) {
+    if (!d || !buf) return -1;
+    return snprintf(buf, len, "%04d-%02d-%02d", d->year, d->month, d->day);
 }
 
-static int days_in_month(int y, int m)
-{
-    static const int d[] = { 31, 28, 31, 30, 31, 30,
-                             31, 31, 30, 31, 30, 31 };
-    if (m < 1 || m > 12)
-        return 0;
-    if (m == 2) {
-        int leap = (y % 4 == 0 && y % 100 != 0) || (y % 400 == 0);
-        return leap ? 29 : 28;
-    }
-    return d[m - 1];
+int date_diff_days(const date_t* from, const date_t* to) {
+    if (!from || !to) return 0;
+    struct tm a = {0}, b = {0};
+    a.tm_year = from->year - 1900; a.tm_mon = from->month - 1; a.tm_mday = from->day;
+    b.tm_year = to->year - 1900; b.tm_mon = to->month - 1; b.tm_mday = to->day;
+    return (int)(difftime(mktime(&b), mktime(&a)) / 86400);
 }
 
-int date_is_valid(const char *yyyymmdd)
-{
-    int y, m, d;
-
-    if (!yyyymmdd || strlen(yyyymmdd) < 8)
-        return 0;
-    if (!is_all_digit(yyyymmdd, 8))
-        return 0;
-
-    y = to_int(yyyymmdd, 4);
-    m = to_int(yyyymmdd + 4, 2);
-    d = to_int(yyyymmdd + 6, 2);
-
-    if (y < 1900 || y > 2999)
-        return 0;
-    if (m < 1 || m > 12)
-        return 0;
-    if (d < 1 || d > days_in_month(y, m))
-        return 0;
-    return 1;
-}
-
-/* Sakamoto 알고리즘: 0=일요일 ... 6=토요일 */
-int date_weekday(const char *yyyymmdd)
-{
-    static const int t[] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };
-    int y, m, d;
-
-    if (!date_is_valid(yyyymmdd))
-        return -1;
-
-    y = to_int(yyyymmdd, 4);
-    m = to_int(yyyymmdd + 4, 2);
-    d = to_int(yyyymmdd + 6, 2);
-
-    if (m < 3)
-        y -= 1;
-    return (y + y / 4 - y / 100 + y / 400 + t[m - 1] + d) % 7;
-}
-
-int date_is_weekend(const char *yyyymmdd)
-{
-    int w = date_weekday(yyyymmdd);
-    return (w == 0 || w == 6) ? 1 : 0;
-}
-
-/* YYYYMMDD 를 하루 증가시킨다 (in==out 허용) */
-static void add_one_day(const char *in, char *out)
-{
-    int y = to_int(in, 4);
-    int m = to_int(in + 4, 2);
-    int d = to_int(in + 6, 2);
-
-    d++;
-    if (d > days_in_month(y, m)) {
-        d = 1;
-        m++;
-        if (m > 12) {
-            m = 1;
-            y++;
-        }
-    }
-    snprintf(out, 9, "%04d%02d%02d", y, m, d);
-}
-
-int date_next_business(const char *yyyymmdd, char *out)
-{
-    char cur[9];
-    int guard = 0;
-
-    if (!date_is_valid(yyyymmdd) || !out)
-        return -1;
-
-    memcpy(cur, yyyymmdd, 8);
-    cur[8] = '\0';
-
-    do {
-        add_one_day(cur, cur);
-        if (++guard > 14)      /* 무한루프 방지 */
-            return -1;
-    } while (date_is_weekend(cur));
-
-    memcpy(out, cur, 8);
-    out[8] = '\0';
+int date_add_days(const date_t* d, int days, date_t* out) {
+    if (!d || !out) return -1;
+    struct tm base = {0};
+    base.tm_year = d->year - 1900; base.tm_mon = d->month - 1; base.tm_mday = d->day;
+    base.tm_mday += days;
+    mktime(&base);
+    out->year = base.tm_year + 1900;
+    out->month = base.tm_mon + 1;
+    out->day = base.tm_mday;
     return 0;
 }
 
-void date_today(char *out)
-{
-    time_t     now = time(NULL);
-    struct tm  tmv;
-    localtime_r(&now, &tmv);
-    strftime(out, 9, "%Y%m%d", &tmv);
+int date_today(date_t* out) {
+    if (!out) return -1;
+    time_t now = time(NULL);
+    struct tm* t = localtime(&now);
+    out->year = t->tm_year + 1900;
+    out->month = t->tm_mon + 1;
+    out->day = t->tm_mday;
+    return 0;
 }