Init will now set the nextUpdateTime to zero

include/ignition/sensors/Sensor.hh

@@ -75,6 +75,9 @@ namespace ignition
       public: virtual bool Load(sdf::ElementPtr _sdf);
 
       /// \brief Initialize values in the sensor
+      /// This will set the next update time to zero. This is particularly
+      /// useful if simulation time has jumped backward, for example during
+      /// a seek backward in a log file.
       public: virtual bool Init();
 
       /// \brief Force the sensor to generate data

src/Sensor.cc

@@ -142,6 +142,7 @@ Sensor::Sensor() :
 //////////////////////////////////////////////////
 bool Sensor::Init()
 {
+  this->dataPtr->nextUpdateTime = std::chrono::steady_clock::duration::zero();
   return true;
 }