diff --git a/src/specificClass.js b/src/specificClass.js
index 23c1289..6378307 100644
--- a/src/specificClass.js
+++ b/src/specificClass.js
@@ -42,7 +42,7 @@ class Reactor {
 
     this.kla = config.kla; // if NaN, use externaly provided OTR [d-1]
 
-    this.currentTime = Date.now(); // milliseconds since epoch [ms]
+    this.currentTime = null; // milliseconds since epoch [ms]
     this.timeStep = 1 / (24*60*60) * this.config.timeStep; // time step in seconds, converted to days.
     this.speedUpFactor = 100; // speed up factor for simulation, 60 means 1 minute per simulated second
   }
@@ -204,8 +204,19 @@ class Reactor {
    * @param {number} newTime - New time to update reactor state to, in milliseconds since epoch.
    */
   updateState(newTime) { // expect update with timestamp
+    if (!this.currentTime) {
+      this.currentTime = newTime;
+      return;
+    }
+
     if (this.upstreamReactor) {
-      this.setInfluent = this.upstreamReactor.getEffluent[0]; // grab main effluent upstream reactor
+      // grab main effluent upstream reactor
+      this.setInfluent = this.upstreamReactor.getEffluent[0];
+    }
+
+    if (newTime === this.currentTime) {
+      // no update necessary
+      return;
     }
 
     const n_iter = Math.floor(this.speedUpFactor * (newTime-this.currentTime) / (this.timeStep*DAY2MS));