diff --git a/lib/blockchain/chain.js b/lib/blockchain/chain.js
index 01122e0c..1c0d2d76 100644
--- a/lib/blockchain/chain.js
+++ b/lib/blockchain/chain.js
@@ -395,6 +395,8 @@ Chain.prototype.verify = async function verify(block, prev, flags) {
   // Ensure the POW is what we expect.
   const bits = await this.getTarget(block.time, prev);
 
+  // console.log(block.bits, bits);
+
   if (block.bits !== bits) {
     throw new VerifyError(block,
       'invalid',
@@ -2278,15 +2280,41 @@ Chain.prototype.getTarget = async function getTarget(time, prev) {
     return pow.bits;
   }
 
+  let retargetInterval, targetSpacing, averagingInterval;
+
+  if (prev.height < pow.blockHeight_version2){
+
+    retargetInterval = pow.retargetInterval_version1;
+    targetSpacing = pow.targetSpacing_version1;
+    averagingInterval = pow.averagingInterval_version1;
+
+  } else if (prev.height >= pow.blockHeight_version2 && prev.height < pow.blockHeight_version3){
+    
+    retargetInterval = pow.retargetInterval_version2;
+    targetSpacing = pow.targetSpacing_version2;
+    averagingInterval = pow.averagingInterval_version2;
+
+  } else if (prev.height >= pow.blockHeight_version3) {
+
+    retargetInterval = pow.retargetInterval_version3;
+    targetSpacing = pow.targetSpacing_version3;
+    averagingInterval = pow.averagingInterval_version3;
+
+  }
+
   // Do not retarget
-  if ((prev.height + 1) % pow.retargetInterval !== 0) {
+  if ((prev.height + 1) % retargetInterval !== 0) {
     if (pow.targetReset) {
       // Special behavior for testnet:
-      if (time > prev.time + pow.targetSpacing * 2)
-        return pow.bits;
+      // console.log("Time: " + time)
+      // console.log("Prev Time: " + prev.time)
+      // console.log("Target Spacing*2: " + (targetSpacing * 2))
+      // console.log("prev+targ: " + (prev.time + targetSpacing * 2))
+      if (time > prev.time + targetSpacing * 2)
+        return prev.bits;
 
       while (prev.height !== 0
-        && prev.height % pow.retargetInterval !== 0
+        && prev.height % retargetInterval !== 0
         && prev.bits === pow.bits) {
         const cache = this.getPrevCache(prev);
 
@@ -2302,11 +2330,11 @@ Chain.prototype.getTarget = async function getTarget(time, prev) {
   }
 
   // Back 6 block
-  var back = pow.averagingInterval - 1;
+  var back = averagingInterval - 1;
 
   
-  if (prev.height + 1 !== pow.averagingInterval)
-    back = pow.averagingInterval;
+  if (prev.height + 1 !== averagingInterval)
+    back = averagingInterval;
 
   
   let first = prev;
@@ -2330,38 +2358,77 @@ Chain.prototype.getTarget = async function getTarget(time, prev) {
 
 Chain.prototype.retarget = function retarget(prev, first) {
   const pow = this.network.pow;
-  const targetTimespan = pow.targetTimespan;
-  const averagingIntervalTimespan = pow.averagingIntervalTimespan;
-  const targetSpacing = pow.targetSpacing;
-  const adjustUp = pow.adjustUp;
-  const adjustDown = pow.adjustDown;
+
+  let height = prev.height;
+
+  let targetTimespan, averagingIntervalTimespan, targetSpacing, adjustUp, adjustDown;
+
+  if (height < pow.blockHeight_version2){
+
+    targetTimespan = pow.targetTimespan_version1;
+    averagingIntervalTimespan = pow.averagingIntervalTimespan_version1;
+    targetSpacing = pow.targetSpacing_version1;
+    adjustUp = pow.adjustUp_version1;
+    adjustDown = pow.adjustDown_version1;
+
+  } else if (height >= pow.blockHeight_version2 && height < pow.blockHeight_version3){
+
+    targetTimespan = pow.targetTimespan_version2;
+    averagingIntervalTimespan = pow.averagingIntervalTimespan_version2;
+    targetSpacing = pow.targetSpacing_version2;
+    adjustUp = pow.adjustUp_version2;
+    adjustDown = pow.adjustDown_version2;
+
+  } else if (height >= pow.blockHeight_version3) {
+
+    targetTimespan = pow.targetTimespan_version3;
+    averagingIntervalTimespan = pow.averagingIntervalTimespan_version3;
+    targetSpacing = pow.targetSpacing_version3;
+    adjustUp = pow.adjustUp_version3;
+    adjustDown = pow.adjustDown_version3;
+
+  } else {
+    // Difficulty NOT handled?!?
+  }
 
   if (pow.noRetargeting)
     return prev.bits;
 
   let actualTimespan = prev.time - first.time;
 
+  // console.log("Actual Timespan: " + actualTimespan);
 
   let minActualTimespan = Math.floor(averagingIntervalTimespan * (100 - adjustUp) / 100)
   let maxActualTimespan = Math.floor(averagingIntervalTimespan * (100 + adjustDown) / 100)
 
+  // console.log("minActualTimespan: " + minActualTimespan);
+  // console.log("maxActualTimespan: " + maxActualTimespan);
+
   if (actualTimespan < minActualTimespan)
     actualTimespan = minActualTimespan;
 
+  // console.log("New Actual Timespan: " + actualTimespan)
 
   if (actualTimespan > maxActualTimespan)
     actualTimespan = maxActualTimespan;
 
+  // console.log("New Actual Timespan: " + actualTimespan)
+
   // Retarget
   let target = consensus.fromCompact(prev.bits);
 
+  // console.log("Target: " + target)
 
   target.imuln(actualTimespan);
+  // console.log("imuln: " + target)
   target.idivn(targetTimespan);
+  // console.log("idivn: " + target)
 
   if (target.gt(pow.limit))
     return pow.bits;
 
+  // console.log("gt: " + target)
+
   return consensus.toCompact(target);
 };
 
diff --git a/lib/protocol/networks.js b/lib/protocol/networks.js
index 59473de3..7edec919 100644
--- a/lib/protocol/networks.js
+++ b/lib/protocol/networks.js
@@ -267,6 +267,30 @@ main.pow = {
 
   adjustDown: 3,
 
+  targetTimespan_version1: 60 * 60,
+  targetSpacing_version1: 40,
+  retargetInterval_version1: (60 * 60) / 40,
+  averagingInterval_version1: (60 * 60) / 40,
+  averagingIntervalTimespan_version1: ((60 * 60) / 40) * 40,
+  adjustUp_version1: 75,
+  adjustDown_version1: 300,
+  blockHeight_version2: 208440,
+  targetTimespan_version2: 15 * 40,
+  targetSpacing_version2: 40,
+  retargetInterval_version2: 15,
+  averagingInterval_version2: 15,
+  averagingIntervalTimespan_version2: 15 * 40,
+  adjustUp_version2: 75,
+  adjustDown_version2: 300,
+  blockHeight_version3: 426000,
+  targetTimespan_version3: 6 * 40,
+  targetSpacing_version3: 40,
+  retargetInterval_version3: 1,
+  averagingInterval_version3: 6,
+  averagingIntervalTimespan_version3: 6 * 40,
+  adjustUp_version3: 2,
+  adjustDown_version3: 3,
+
   /**
    * Whether to reset target if a block
    * has not been mined recently.
@@ -578,9 +602,29 @@ testnet.pow = {
     '000000000000000000000000000000000000000000000000000000083540886d',
     'hex'
   ),
-  targetTimespan: 3.5 * 24 * 60 * 60,
-  targetSpacing: 40,
-  retargetInterval: 1,
+  targetTimespan_version1: 60 * 60,
+  targetSpacing_version1: 40,
+  retargetInterval_version1: (60 * 60) / 40,
+  averagingInterval_version1: (60 * 60) / 40,
+  averagingIntervalTimespan_version1: ((60 * 60) / 40) * 40,
+  adjustUp_version1: 75,
+  adjustDown_version1: 300,
+  blockHeight_version2: 50000,
+  targetTimespan_version2: 15 * 40,
+  targetSpacing_version2: 40,
+  retargetInterval_version2: 15,
+  averagingInterval_version2: 15,
+  averagingIntervalTimespan_version2: 15 * 40,
+  adjustUp_version2: 75,
+  adjustDown_version2: 300,
+  blockHeight_version3: 60000,
+  targetTimespan_version3: 6 * 40,
+  targetSpacing_version3: 40,
+  retargetInterval_version3: 1,
+  averagingInterval_version3: 6,
+  averagingIntervalTimespan_version3: 6 * 40,
+  adjustUp_version3: 2,
+  adjustDown_version3: 3,
   targetReset: true,
   noRetargeting: false
 };