diff --git a/include/tanabata.h b/include/tanabata.h
index 5b6e528..fe8b3d5 100644
--- a/include/tanabata.h
+++ b/include/tanabata.h
@@ -20,9 +20,9 @@ typedef struct tanabata {
     Sasahyou   sasahyou;      // Sasahyou struct
     Sappyou    sappyou;       // Sappyou struct
     Shoppyou   shoppyou;      // Shoppyou struct
-    _Bool      sasahyou_mod;  // Sasahyou modified flag
-    _Bool      sappyou_mod;   // Sappyou modified flag
-    _Bool      shoppyou_mod;  // Shoppyou modified flag
+    uint64_t   sasahyou_mod;  // Sasahyou file last modificaton timestamp
+    uint64_t   sappyou_mod;   // Sappyou file last modificaton timestamp
+    uint64_t   shoppyou_mod;  // Shoppyou file last modificaton timestamp
 } Tanabata;
 
 // ==================== DATABASE SECTION ==================== //
diff --git a/lib/database.c b/lib/database.c
index f10ce59..c5093b6 100644
--- a/lib/database.c
+++ b/lib/database.c
@@ -1,6 +1,7 @@
 #include <malloc.h>
 #include <string.h>
 #include <sys/stat.h>
+#include <time.h>
 
 #include "../include/tanabata.h"
 
@@ -14,9 +15,9 @@ int tanabata_init(Tanabata *tanabata) {
     if (shoppyou_init(&tanabata->shoppyou) != 0) {
         return 1;
     }
-    tanabata->sasahyou_mod = 1;
-    tanabata->sappyou_mod = 1;
-    tanabata->shoppyou_mod = 1;
+    tanabata->sasahyou_mod = 0;
+    tanabata->sappyou_mod = 0;
+    tanabata->shoppyou_mod = 0;
     return 0;
 }
 
@@ -36,8 +37,8 @@ int tanabata_free(Tanabata *tanabata) {
 int tanabata_weed(Tanabata *tanabata) {
     uint64_t hole_cnt;
     uint64_t new_id;
-    Kazari *current_kazari;
     if (tanabata->shoppyou.hole_cnt > 0) {
+        Kazari *current_kazari;
         hole_cnt = 0;
         current_kazari = tanabata->shoppyou.database;
         for (uint64_t i = 0; i < tanabata->shoppyou.size; i++) {
@@ -54,7 +55,7 @@ int tanabata_weed(Tanabata *tanabata) {
         tanabata->shoppyou.hole_cnt = 0;
         free(tanabata->shoppyou.holes);
         tanabata->shoppyou.database = realloc(tanabata->shoppyou.database, tanabata->shoppyou.size * sizeof(Kazari));
-        tanabata->shoppyou_mod = 1;
+        tanabata->shoppyou.modified_ts = time(NULL);
     }
     if (tanabata->sasahyou.hole_cnt > 0) {
         hole_cnt = 0;
@@ -76,7 +77,7 @@ int tanabata_weed(Tanabata *tanabata) {
         tanabata->sasahyou.hole_cnt = 0;
         free(tanabata->sasahyou.holes);
         tanabata->sasahyou.database = realloc(tanabata->sasahyou.database, tanabata->sasahyou.size * sizeof(Sasa));
-        tanabata->sasahyou_mod = 1;
+        tanabata->sasahyou.modified_ts = time(NULL);
     }
     if (tanabata->sappyou.hole_cnt > 0) {
         hole_cnt = 0;
@@ -98,7 +99,7 @@ int tanabata_weed(Tanabata *tanabata) {
         tanabata->sappyou.hole_cnt = 0;
         free(tanabata->sappyou.holes);
         tanabata->sappyou.database = realloc(tanabata->sappyou.database, tanabata->sappyou.size * sizeof(Tanzaku));
-        tanabata->sappyou_mod = 1;
+        tanabata->sappyou.modified_ts = time(NULL);
     }
     return 0;
 }
@@ -113,25 +114,25 @@ int tanabata_load(Tanabata *tanabata) {
     if (shoppyou_load(&tanabata->shoppyou) != 0) {
         return 1;
     }
-    tanabata->sasahyou_mod = 0;
-    tanabata->sappyou_mod = 0;
-    tanabata->shoppyou_mod = 0;
+    tanabata->sasahyou_mod = tanabata->sasahyou.modified_ts;
+    tanabata->sappyou_mod = tanabata->sappyou.modified_ts;
+    tanabata->shoppyou_mod = tanabata->shoppyou.modified_ts;
     return 0;
 }
 
 int tanabata_save(Tanabata *tanabata) {
-    if (tanabata->sasahyou_mod && sasahyou_save(&tanabata->sasahyou) != 0) {
+    if (tanabata->sasahyou_mod != tanabata->sasahyou.modified_ts && sasahyou_save(&tanabata->sasahyou) != 0) {
         return 1;
     }
-    if (tanabata->sappyou_mod && sappyou_save(&tanabata->sappyou) != 0) {
+    if (tanabata->sappyou_mod != tanabata->sappyou.modified_ts && sappyou_save(&tanabata->sappyou) != 0) {
         return 1;
     }
-    if (tanabata->shoppyou_mod && shoppyou_save(&tanabata->shoppyou) != 0) {
+    if (tanabata->shoppyou_mod != tanabata->shoppyou.modified_ts && shoppyou_save(&tanabata->shoppyou) != 0) {
         return 1;
     }
-    tanabata->sasahyou_mod = 0;
-    tanabata->sappyou_mod = 0;
-    tanabata->shoppyou_mod = 0;
+    tanabata->sasahyou_mod = tanabata->sasahyou.modified_ts;
+    tanabata->sappyou_mod = tanabata->sappyou.modified_ts;
+    tanabata->shoppyou_mod = tanabata->shoppyou.modified_ts;
     return 0;
 }
 
@@ -154,9 +155,9 @@ int tanabata_open(Tanabata *tanabata, const char *path) {
         return 1;
     }
     free(file_path);
-    tanabata->sasahyou_mod = 0;
-    tanabata->sappyou_mod = 0;
-    tanabata->shoppyou_mod = 0;
+    tanabata->sasahyou_mod = tanabata->sasahyou.modified_ts;
+    tanabata->sappyou_mod = tanabata->sappyou.modified_ts;
+    tanabata->shoppyou_mod = tanabata->shoppyou.modified_ts;
     return 0;
 }
 
@@ -166,26 +167,26 @@ int tanabata_dump(Tanabata *tanabata, const char *path) {
         return 1;
     }
     char *file_path = malloc(strlen(path) + 10);
-    if (tanabata->sasahyou_mod) {
+    if (tanabata->sasahyou_mod != tanabata->sasahyou.modified_ts) {
         strcpy(file_path, path);
         if (sasahyou_dump(&tanabata->sasahyou, strcat(file_path, "/sasahyou")) != 0) {
             return 1;
         }
-        tanabata->sasahyou_mod = 0;
+        tanabata->sasahyou_mod = tanabata->sasahyou.modified_ts;
     }
-    if (tanabata->sappyou_mod) {
+    if (tanabata->sappyou_mod != tanabata->sappyou.modified_ts) {
         strcpy(file_path, path);
         if (sappyou_dump(&tanabata->sappyou, strcat(file_path, "/sappyou")) != 0) {
             return 1;
         }
-        tanabata->sappyou_mod = 0;
+        tanabata->sappyou_mod = tanabata->sappyou.modified_ts;
     }
-    if (tanabata->shoppyou_mod) {
+    if (tanabata->shoppyou_mod != tanabata->shoppyou.modified_ts) {
         strcpy(file_path, path);
         if (shoppyou_dump(&tanabata->shoppyou, strcat(file_path, "/shoppyou")) != 0) {
             return 1;
         }
-        tanabata->shoppyou_mod = 0;
+        tanabata->shoppyou_mod = tanabata->shoppyou.modified_ts;
     }
     free(file_path);
     return 0;
diff --git a/lib/sasa.c b/lib/sasa.c
index 360c3d7..06a40c3 100644
--- a/lib/sasa.c
+++ b/lib/sasa.c
@@ -16,9 +16,8 @@ int tanabata_sasa_add(Tanabata *tanabata, const char *path) {
     }
     char *abspath = NULL;
     abspath = realpath(path, abspath);
-    if (abspath != NULL && sasa_add(&tanabata->sasahyou, abspath) == 0) {
-        tanabata->sasahyou_mod = 1;
-        return 0;
+    if (abspath != NULL) {
+        return sasa_add(&tanabata->sasahyou, abspath);
     }
     return 1;
 }
@@ -29,7 +28,6 @@ int tanabata_sasa_rem_by_id(Tanabata *tanabata, uint64_t sasa_id) {
     }
     if (sasa_rem(&tanabata->sasahyou, sasa_id) == 0 &&
         kazari_rem_by_sasa(&tanabata->shoppyou, sasa_id) == 0) {
-        tanabata->sasahyou_mod = 1;
         return 0;
     }
     return 1;
@@ -41,7 +39,6 @@ int tanabata_sasa_rem_by_path(Tanabata *tanabata, const char *path) {
         if (current_sasa->id != HOLE_ID && strcmp(current_sasa->path, path) == 0) {
             if (sasa_rem(&tanabata->sasahyou, current_sasa->id) == 0 &&
                 kazari_rem_by_sasa(&tanabata->shoppyou, current_sasa->id) == 0) {
-                tanabata->sasahyou_mod = 1;
                 return 0;
             }
             return 1;
diff --git a/lib/tanzaku.c b/lib/tanzaku.c
index 7ad981e..9fa01d8 100644
--- a/lib/tanzaku.c
+++ b/lib/tanzaku.c
@@ -13,11 +13,7 @@ int tanabata_tanzaku_add(Tanabata *tanabata, const char *name, const char *descr
         }
         current_tanzaku++;
     }
-    if (tanzaku_add(&tanabata->sappyou, name, description) == 0) {
-        tanabata->sappyou_mod = 1;
-        return 0;
-    }
-    return 1;
+    return tanzaku_add(&tanabata->sappyou, name, description);
 }
 
 int tanabata_tanzaku_rem_by_id(Tanabata *tanabata, uint64_t tanzaku_id) {
@@ -26,7 +22,6 @@ int tanabata_tanzaku_rem_by_id(Tanabata *tanabata, uint64_t tanzaku_id) {
     }
     if (tanzaku_rem(&tanabata->sappyou, tanzaku_id) == 0 &&
         kazari_rem_by_tanzaku(&tanabata->shoppyou, tanzaku_id) == 0) {
-        tanabata->sappyou_mod = 1;
         return 0;
     }
     return 1;
@@ -38,7 +33,6 @@ int tanabata_tanzaku_rem_by_name(Tanabata *tanabata, const char *name) {
         if (current_tanzaku->id != HOLE_ID && strcmp(current_tanzaku->name, name) == 0) {
             if (tanzaku_rem(&tanabata->sappyou, current_tanzaku->id) == 0 &&
                 kazari_rem_by_tanzaku(&tanabata->shoppyou, current_tanzaku->id) == 0) {
-                tanabata->sappyou_mod = 1;
                 return 0;
             }
             return 1;