diff --git a/library/include/mobilisis/tariff_time_range.h b/library/include/mobilisis/tariff_time_range.h
index 87b6bd1..6201778 100644
--- a/library/include/mobilisis/tariff_time_range.h
+++ b/library/include/mobilisis/tariff_time_range.h
@@ -7,8 +7,8 @@
 /// Time range definition
 /// </summary>
 class TariffTimeRange {
-    QTime m_time_from;
-    QTime m_time_until;
+    QTime m_time_from;  // if m_time_from == m_time_until, then the time range
+    QTime m_time_until; // actually is the time point m_time_from
 
 public: