diff --git a/data.py b/data.py
index 1471e1f..3edc58a 100644
--- a/data.py
+++ b/data.py
@@ -160,6 +160,9 @@ class Report:
         self._data = data
         self._date = pdate
         self._actual_data_len = 0
+        self._prev = None
+        self._next = None
+        self._update_prev_next()
 
     def report(self):
         tmp = []
@@ -223,18 +226,36 @@ class Report:
         month[self._date.strftime("%d")] = save_list
         self._data[self._date.strftime("%Y-%m")] = month
 
+    def _update_prev_next(self):
+        self._prev = None
+        self._next = None
+        for i in range(1, 32):
+            new_date = self._date - timedelta(days=i)
+            if new_date.strftime("%Y-%m") not in self._data:
+                break
+            if new_date.strftime("%d") in self._data[new_date.strftime("%Y-%m")]:
+                self._prev = new_date
+                break
+        for i in range(1, 32):
+            new_date = self._date + timedelta(days=i)
+            if new_date > date.today():
+                break
+            if new_date.strftime("%Y-%m") not in self._data:
+                break
+            if new_date.strftime("%d") in self._data[new_date.strftime("%Y-%m")]:
+                self._next = new_date
+                break
+
     def prev_next_avail(self):
-        if self._date.strftime("%Y-%m") not in self._data:
-            return False, False
-        prev = (self._date - timedelta(days=1)).strftime("%d") in self._data[self._date.strftime("%Y-%m")]
-        _next = (self._date + timedelta(days=1)).strftime("%d") in self._data[self._date.strftime("%Y-%m")]
-        return prev, _next
+        return self._prev is not None, self._next is not None
 
     def previous(self):
-        self._date = self._date - timedelta(days=1)
+        self._date = self._prev
+        self._update_prev_next()
 
     def next(self):
-        self._date = self._date + timedelta(days=1)
+        self._date = self._next
+        self._update_prev_next()
 
     def date(self):
         return self._date.strftime("%Y-%m-%d")