Uses external MongoDB, uses dates instead of strings for timestamps

src/main/java/com/henrypump/poc/Measurement.java

@@ -2,7 +2,9 @@ package com.henrypump.poc;
 
 import org.bson.Document;
 
+import java.time.ZoneId;
 import java.time.ZonedDateTime;
+import java.util.Date;
 
 import static java.lang.Math.abs;
 
@@ -44,7 +46,9 @@ public class Measurement {
 
         Document lastStored =  this.db.getLastStoredMeasurement(this.tagName);
         try {
-            ZonedDateTime timestamp = ZonedDateTime.parse((CharSequence) lastStored.get("timestamp"));
+            Date lastStoredTimestamp = (Date) lastStored.get("timestamp");
+            ZonedDateTime timestamp = ZonedDateTime.ofInstant(lastStoredTimestamp.toInstant(),
+                    ZoneId.systemDefault());
             if (isToday(timestamp)){
                 this.average = lastStored.getDouble("dailyAverage");
                 this.total = lastStored.getDouble("dailyTotal");