diff --git a/reactor.py b/reactor.py
index 05ba79e..356a986 100644
--- a/reactor.py
+++ b/reactor.py
@@ -22,7 +22,7 @@ class Glimpse():
             self.is_initialized = 1
             self.total_num = len(self.elt_u.electrons)
             for i in self.elt_u.electrons:
-                if i['next_date'] != 0:
+                if i['next_date'] > 0:
                     self.next_date = min(self.next_date, i['next_date'])
                 self.lastest_date = max(self.lastest_date, i['last_date'])
                 if i['is_activated']: