diff --git a/native/jni/src/suggest/core/policy/dictionary_header_structure_policy.h b/native/jni/src/suggest/core/policy/dictionary_header_structure_policy.h
index a6829b4..5492c60 100644
--- a/native/jni/src/suggest/core/policy/dictionary_header_structure_policy.h
+++ b/native/jni/src/suggest/core/policy/dictionary_header_structure_policy.h
@@ -37,6 +37,8 @@
 
     virtual float getMultiWordCostMultiplier() const = 0;
 
+    virtual int getLastDecayedTime() const = 0;
+
     virtual void readHeaderValueOrQuestionMark(const char *const key, int *outValue,
             int outValueSize) const = 0;
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.cpp
index 8753c6e..b1170e2 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.cpp
@@ -360,13 +360,13 @@
 }
 
 bool DynamicBigramListPolicy::updateProbabilityForDecay(
-        BigramListReadWriteUtils::BigramFlags bigramFlags, const int targetPtNodePos,
+        const BigramListReadWriteUtils::BigramFlags bigramFlags, const int targetPtNodePos,
         int *const bigramEntryPos, bool *const outRemoved) const {
     *outRemoved = false;
     if (mIsDecayingDict) {
         // Update bigram probability for decaying.
         const int newProbability = ForgettingCurveUtils::getEncodedProbabilityToSave(
-                BigramListReadWriteUtils::getProbabilityFromFlags(bigramFlags));
+                BigramListReadWriteUtils::getProbabilityFromFlags(bigramFlags), mHeaderPolicy);
         if (ForgettingCurveUtils::isValidEncodedProbability(newProbability)) {
             // Write new probability.
             const BigramListReadWriteUtils::BigramFlags updatedBigramFlags =
diff --git a/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h b/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h
index b358b4e..0504b59 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/bigram/dynamic_bigram_list_policy.h
@@ -27,6 +27,7 @@
 namespace latinime {
 
 class BufferWithExtendableBuffer;
+class DictionaryHeaderStructurePolicy;
 class DictionaryShortcutsStructurePolicy;
 
 /*
@@ -34,10 +35,12 @@
  */
 class DynamicBigramListPolicy : public DictionaryBigramsStructurePolicy {
  public:
-    DynamicBigramListPolicy(BufferWithExtendableBuffer *const buffer,
+    DynamicBigramListPolicy(const DictionaryHeaderStructurePolicy *const headerPolicy,
+            BufferWithExtendableBuffer *const buffer,
             const DictionaryShortcutsStructurePolicy *const shortcutPolicy,
             const bool isDecayingDict)
-            : mBuffer(buffer), mShortcutPolicy(shortcutPolicy), mIsDecayingDict(isDecayingDict) {}
+            : mHeaderPolicy(headerPolicy), mBuffer(buffer), mShortcutPolicy(shortcutPolicy),
+              mIsDecayingDict(isDecayingDict) {}
 
     ~DynamicBigramListPolicy() {}
 
@@ -74,6 +77,7 @@
     static const int CONTINUING_BIGRAM_LINK_COUNT_LIMIT;
     static const int BIGRAM_ENTRY_COUNT_IN_A_BIGRAM_LIST_LIMIT;
 
+    const DictionaryHeaderStructurePolicy *const mHeaderPolicy;
     BufferWithExtendableBuffer *const mBuffer;
     const DictionaryShortcutsStructurePolicy *const mShortcutPolicy;
     const bool mIsDecayingDict;
@@ -81,7 +85,7 @@
     // Follow bigram link and return the position of bigram target PtNode that is currently valid.
     int followBigramLinkAndGetCurrentBigramPtNodePos(const int originalBigramPos) const;
 
-    bool updateProbabilityForDecay(BigramListReadWriteUtils::BigramFlags bigramFlags,
+    bool updateProbabilityForDecay(const BigramListReadWriteUtils::BigramFlags bigramFlags,
             const int targetPtNodePos, int *const bigramEntryPos, bool *const outRemoved) const;
 };
 } // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp
index 324b530..a17a0ac 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.cpp
@@ -16,6 +16,7 @@
 
 #include "suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h"
 
+#include "suggest/core/policy/dictionary_header_structure_policy.h"
 #include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
 
 namespace latinime {
@@ -29,7 +30,8 @@
     bool isUselessPtNode = !node->isTerminal();
     if (node->isTerminal() && mIsDecayingDict) {
         const int newProbability =
-                ForgettingCurveUtils::getEncodedProbabilityToSave(node->getProbability());
+                ForgettingCurveUtils::getEncodedProbabilityToSave(node->getProbability(),
+                        mHeaderPolicy);
         int writingPos = node->getProbabilityFieldPos();
         // Update probability.
         if (!DynamicPatriciaTrieWritingUtils::writeProbabilityAndAdvancePosition(
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h
index 463715a..3ca2f2a 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_gc_event_listeners.h
@@ -29,6 +29,8 @@
 
 namespace latinime {
 
+class DictionaryHeaderStructurePolicy;
+
 class DynamicPatriciaTrieGcEventListeners {
  public:
     // Updates all PtNodes that can be reached from the root. Checks if each PtNode is useless or
@@ -38,10 +40,12 @@
         : public DynamicPatriciaTrieReadingHelper::TraversingEventListener {
      public:
         TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted(
+                const DictionaryHeaderStructurePolicy *const headerPolicy,
                 DynamicPatriciaTrieWritingHelper *const writingHelper,
                 BufferWithExtendableBuffer *const buffer, const bool isDecayingDict)
-                : mWritingHelper(writingHelper), mBuffer(buffer), mIsDecayingDict(isDecayingDict),
-                  mValueStack(), mChildrenValue(0), mValidUnigramCount(0) {}
+                : mHeaderPolicy(headerPolicy), mWritingHelper(writingHelper), mBuffer(buffer),
+                  mIsDecayingDict(isDecayingDict), mValueStack(), mChildrenValue(0),
+                  mValidUnigramCount(0) {}
 
         ~TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted() {};
 
@@ -72,9 +76,10 @@
         DISALLOW_IMPLICIT_CONSTRUCTORS(
                 TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted);
 
+        const DictionaryHeaderStructurePolicy *const mHeaderPolicy;
         DynamicPatriciaTrieWritingHelper *const mWritingHelper;
         BufferWithExtendableBuffer *const mBuffer;
-        const int mIsDecayingDict;
+        const bool mIsDecayingDict;
         std::vector<int> mValueStack;
         int mChildrenValue;
         int mValidUnigramCount;
@@ -85,7 +90,8 @@
     class TraversePolicyToUpdateBigramProbability
             : public DynamicPatriciaTrieReadingHelper::TraversingEventListener {
      public:
-        TraversePolicyToUpdateBigramProbability(DynamicBigramListPolicy *const bigramPolicy)
+        TraversePolicyToUpdateBigramProbability(
+                DynamicBigramListPolicy *const bigramPolicy)
                 : mBigramPolicy(bigramPolicy), mValidBigramEntryCount(0) {}
 
         bool onAscend() { return true; }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp
index 60d0db0..31e3fb4 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp
@@ -42,7 +42,6 @@
 const int DynamicPatriciaTriePolicy::MAX_DICT_EXTENDED_REGION_SIZE = 1024 * 1024;
 const int DynamicPatriciaTriePolicy::MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS =
         DynamicPatriciaTrieWritingHelper::MAX_DICTIONARY_SIZE - 1024;
-const int DynamicPatriciaTriePolicy::DECAY_INTERVAL_FOR_DECAYING_DICTS = 2 * 60 * 60;
 
 void DynamicPatriciaTriePolicy::createAndGetAllChildNodes(const DicNode *const dicNode,
         DicNodeVector *const childDicNodes) const {
@@ -314,15 +313,15 @@
         AKLOGI("Warning: flushWithGC() is called for non-updatable dictionary.");
         return;
     }
-    const bool runGCwithDecay = needsToDecay();
-    DynamicBigramListPolicy bigramListPolicyForGC(&mBufferWithExtendableBuffer,
-            &mShortcutListPolicy, runGCwithDecay);
+    const bool needsToDecay = mHeaderPolicy.isDecayingDict()
+            && (mNeedsToDecayForTesting || ForgettingCurveUtils::needsToDecay(
+                    false /* mindsBlockByDecay */, mUnigramCount, mBigramCount, &mHeaderPolicy));
+    DynamicBigramListPolicy bigramListPolicyForGC(&mHeaderPolicy, &mBufferWithExtendableBuffer,
+            &mShortcutListPolicy, needsToDecay);
     DynamicPatriciaTrieWritingHelper writingHelper(&mBufferWithExtendableBuffer,
-            &bigramListPolicyForGC, &mShortcutListPolicy, runGCwithDecay);
+            &bigramListPolicyForGC, &mShortcutListPolicy, needsToDecay);
     writingHelper.writeToDictFileWithGC(getRootPosition(), filePath, &mHeaderPolicy);
-    if (runGCwithDecay) {
-        mNeedsToDecayForTesting = false;
-    }
+    mNeedsToDecayForTesting = false;
 }
 
 bool DynamicPatriciaTriePolicy::needsToRunGC(const bool mindsBlockByGC) const {
@@ -344,16 +343,8 @@
         // Needs to reduce dictionary size.
         return true;
     } else if (mHeaderPolicy.isDecayingDict()) {
-        if (mUnigramCount >= ForgettingCurveUtils::MAX_UNIGRAM_COUNT) {
-            // Unigram count exceeds the limit.
-            return true;
-        } else if (mBigramCount >= ForgettingCurveUtils::MAX_BIGRAM_COUNT) {
-            // Bigram count exceeds the limit.
-            return true;
-        } else if (mindsBlockByGC && needsToDecay()) {
-            // Time to update probabilities for decaying.
-            return true;
-        }
+        return mNeedsToDecayForTesting || ForgettingCurveUtils::needsToDecay(
+                mindsBlockByGC, mUnigramCount, mBigramCount, &mHeaderPolicy);
     }
     return false;
 }
@@ -369,9 +360,4 @@
     }
 }
 
-bool DynamicPatriciaTriePolicy::needsToDecay() const {
-    return mHeaderPolicy.isDecayingDict() && (mNeedsToDecayForTesting
-            || mHeaderPolicy.getLastDecayedTime() + DECAY_INTERVAL_FOR_DECAYING_DICTS < time(0));
-}
-
 } // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
index c3bbe99..903f65e 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
@@ -37,7 +37,7 @@
               mBufferWithExtendableBuffer(mBuffer->getBuffer() + mHeaderPolicy.getSize(),
                       mBuffer->getBufferSize() - mHeaderPolicy.getSize()),
               mShortcutListPolicy(&mBufferWithExtendableBuffer),
-              mBigramListPolicy(&mBufferWithExtendableBuffer, &mShortcutListPolicy,
+              mBigramListPolicy(&mHeaderPolicy, &mBufferWithExtendableBuffer, &mShortcutListPolicy,
                       mHeaderPolicy.isDecayingDict()),
               mUnigramCount(mHeaderPolicy.getUnigramCount()),
               mBigramCount(mHeaderPolicy.getBigramCount()), mNeedsToDecayForTesting(false) {}
@@ -105,7 +105,6 @@
     static const char *const SET_NEEDS_TO_DECAY_FOR_TESTING_QUERY;
     static const int MAX_DICT_EXTENDED_REGION_SIZE;
     static const int MIN_DICT_SIZE_TO_REFUSE_DYNAMIC_OPERATIONS;
-    static const int DECAY_INTERVAL_FOR_DECAYING_DICTS;
 
     const MmappedBuffer *const mBuffer;
     const HeaderPolicy mHeaderPolicy;
@@ -115,8 +114,6 @@
     int mUnigramCount;
     int mBigramCount;
     int mNeedsToDecayForTesting;
-
-    bool needsToDecay() const;
 };
 } // namespace latinime
 #endif // LATINIME_DYNAMIC_PATRICIA_TRIE_POLICY_H
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp
index 70a9ee5..067c8ec 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.cpp
@@ -165,7 +165,10 @@
             MAX_DICTIONARY_SIZE);
     int unigramCount = 0;
     int bigramCount = 0;
-    if (!runGC(rootPtNodeArrayPos, &newDictBuffer, &unigramCount, &bigramCount)) {
+    if (mNeedsToDecay) {
+        ForgettingCurveUtils::sTimeKeeper.setCurrentTime();
+    }
+    if (!runGC(rootPtNodeArrayPos, headerPolicy, &newDictBuffer, &unigramCount, &bigramCount)) {
         return;
     }
     BufferWithExtendableBuffer headerBuffer(0 /* originalBuffer */, 0 /* originalBufferSize */);
@@ -481,14 +484,14 @@
 }
 
 bool DynamicPatriciaTrieWritingHelper::runGC(const int rootPtNodeArrayPos,
-        BufferWithExtendableBuffer *const bufferToWrite, int *const outUnigramCount,
-        int *const outBigramCount) {
+        const HeaderPolicy *const headerPolicy, BufferWithExtendableBuffer *const bufferToWrite,
+        int *const outUnigramCount, int *const outBigramCount) {
     DynamicPatriciaTrieReadingHelper readingHelper(mBuffer, mBigramPolicy, mShortcutPolicy);
     readingHelper.initWithPtNodeArrayPos(rootPtNodeArrayPos);
     DynamicPatriciaTrieGcEventListeners
             ::TraversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted
                     traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted(
-                            this, mBuffer, mNeedsToDecay);
+                            headerPolicy, this, mBuffer, mNeedsToDecay);
     if (!readingHelper.traverseAllPtNodesInPostorderDepthFirstManner(
             &traversePolicyToUpdateUnigramProbabilityAndMarkUselessPtNodesAsDeleted)) {
         return false;
@@ -505,7 +508,6 @@
             &traversePolicyToUpdateBigramProbability)) {
         return false;
     }
-
     if (mNeedsToDecay && traversePolicyToUpdateBigramProbability.getValidBigramEntryCount()
             > ForgettingCurveUtils::MAX_BIGRAM_COUNT_AFTER_GC) {
         // TODO: Remove more bigrams.
@@ -524,7 +526,7 @@
 
     // Create policy instance for the GCed dictionary.
     DynamicShortcutListPolicy newDictShortcutPolicy(bufferToWrite);
-    DynamicBigramListPolicy newDictBigramPolicy(bufferToWrite, &newDictShortcutPolicy,
+    DynamicBigramListPolicy newDictBigramPolicy(headerPolicy, bufferToWrite, &newDictShortcutPolicy,
             mNeedsToDecay);
     // Create reading helper for the GCed dictionary.
     DynamicPatriciaTrieReadingHelper newDictReadingHelper(bufferToWrite, &newDictBigramPolicy,
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h
index 0caf291..ca86647 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_writing_helper.h
@@ -128,8 +128,9 @@
             const int probabilityOfNewPtNode, const int *const newNodeCodePoints,
             const int newNodeCodePointCount);
 
-    bool runGC(const int rootPtNodeArrayPos, BufferWithExtendableBuffer *const bufferToWrite,
-            int *const outUnigramCount, int *const outBigramCount);
+    bool runGC(const int rootPtNodeArrayPos, const HeaderPolicy *const headerPolicy,
+            BufferWithExtendableBuffer *const bufferToWrite, int *const outUnigramCount,
+            int *const outBigramCount);
 
     int getUpdatedProbability(const int originalProbability, const int newProbability);
 };
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.cpp b/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.cpp
index b502fe2..19ca354 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.cpp
@@ -15,10 +15,12 @@
  */
 
 #include <cmath>
+#include <ctime>
 #include <stdlib.h>
 
 #include "suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h"
 
+#include "suggest/core/policy/dictionary_header_structure_policy.h"
 #include "suggest/policyimpl/dictionary/utils/probability_utils.h"
 
 namespace latinime {
@@ -35,8 +37,14 @@
 // Currently, we try to decay each uni/bigram once every 2 hours. Accordingly, the expected
 // duration of the decay is approximately 66hours.
 const float ForgettingCurveUtils::MIN_PROBABILITY_TO_DECAY = 0.03f;
+const int ForgettingCurveUtils::DECAY_INTERVAL_SECONDS = 2 * 60 * 60;
 
 const ForgettingCurveUtils::ProbabilityTable ForgettingCurveUtils::sProbabilityTable;
+ForgettingCurveUtils::TimeKeeper ForgettingCurveUtils::sTimeKeeper;
+
+void ForgettingCurveUtils::TimeKeeper::setCurrentTime() {
+    mCurrentTime = time(0);
+}
 
 /* static */ int ForgettingCurveUtils::getProbability(const int encodedUnigramProbability,
         const int encodedBigramProbability) {
@@ -76,19 +84,44 @@
     return encodedProbability >= MIN_VALID_ENCODED_PROBABILITY;
 }
 
-/* static */ int ForgettingCurveUtils::getEncodedProbabilityToSave(const int encodedProbability) {
-    const int currentEncodedProbability = max(min(encodedProbability, MAX_ENCODED_PROBABILITY), 0);
+/* static */ int ForgettingCurveUtils::getEncodedProbabilityToSave(const int encodedProbability,
+        const DictionaryHeaderStructurePolicy *const headerPolicy) {
+    const int elapsedTime = sTimeKeeper.peekCurrentTime() - headerPolicy->getLastDecayedTime();
+    const int decayIterationCount = max(elapsedTime / DECAY_INTERVAL_SECONDS, 1);
+    int currentEncodedProbability = max(min(encodedProbability, MAX_ENCODED_PROBABILITY), 0);
     // TODO: Implement the decay in more proper way.
-    const float currentRate = static_cast<float>(currentEncodedProbability)
-            / static_cast<float>(MAX_ENCODED_PROBABILITY);
-    const float thresholdToDecay = MIN_PROBABILITY_TO_DECAY
-            + (1.0f - MIN_PROBABILITY_TO_DECAY) * (1.0f - currentRate);
-    const float randValue = static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
-    if (thresholdToDecay < randValue) {
-        return max(currentEncodedProbability - ENCODED_PROBABILITY_STEP, 0);
-    } else {
-        return currentEncodedProbability;
+    for (int i = 0; i < decayIterationCount; ++i) {
+        const float currentRate = static_cast<float>(currentEncodedProbability)
+                / static_cast<float>(MAX_ENCODED_PROBABILITY);
+        const float thresholdToDecay = MIN_PROBABILITY_TO_DECAY
+                + (1.0f - MIN_PROBABILITY_TO_DECAY) * currentRate;
+        const float randValue = static_cast<float>(rand()) / static_cast<float>(RAND_MAX);
+        if (thresholdToDecay < randValue) {
+            currentEncodedProbability = max(currentEncodedProbability - ENCODED_PROBABILITY_STEP,
+                    0);
+        }
     }
+    return currentEncodedProbability;
+}
+
+/* static */ bool ForgettingCurveUtils::needsToDecay(const bool mindsBlockByDecay,
+        const int unigramCount, const int bigramCount,
+        const DictionaryHeaderStructurePolicy *const headerPolicy) {
+    if (unigramCount >= ForgettingCurveUtils::MAX_UNIGRAM_COUNT) {
+        // Unigram count exceeds the limit.
+        return true;
+    } else if (bigramCount >= ForgettingCurveUtils::MAX_BIGRAM_COUNT) {
+        // Bigram count exceeds the limit.
+        return true;
+    }
+    if (mindsBlockByDecay) {
+        return false;
+    }
+    if (headerPolicy->getLastDecayedTime() + DECAY_INTERVAL_SECONDS < time(0)) {
+        // Time to decay.
+        return true;
+    }
+    return false;
 }
 
 /* static */ int ForgettingCurveUtils::decodeProbability(const int encodedProbability) {
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h b/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h
index d666f22..2ad4238 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/forgetting_curve_utils.h
@@ -23,16 +23,32 @@
 
 namespace latinime {
 
+class DictionaryHeaderStructurePolicy;
+
 // TODO: Check the elapsed time and decrease the probability depending on the time. Time field is
 // required to introduced to each terminal PtNode and bigram entry.
 // TODO: Quit using bigram probability to indicate the delta.
 class ForgettingCurveUtils {
  public:
+    class TimeKeeper {
+     public:
+        TimeKeeper() : mCurrentTime(0) {}
+        void setCurrentTime();
+        int peekCurrentTime() const { return mCurrentTime; };
+
+     private:
+        DISALLOW_COPY_AND_ASSIGN(TimeKeeper);
+
+        int mCurrentTime;
+    };
+
     static const int MAX_UNIGRAM_COUNT;
     static const int MAX_UNIGRAM_COUNT_AFTER_GC;
     static const int MAX_BIGRAM_COUNT;
     static const int MAX_BIGRAM_COUNT_AFTER_GC;
 
+    static TimeKeeper sTimeKeeper;
+
     static int getProbability(const int encodedUnigramProbability,
             const int encodedBigramProbability);
 
@@ -41,7 +57,11 @@
 
     static int isValidEncodedProbability(const int encodedProbability);
 
-    static int getEncodedProbabilityToSave(const int encodedProbability);
+    static int getEncodedProbabilityToSave(const int encodedProbability,
+            const DictionaryHeaderStructurePolicy *const headerPolicy);
+
+    static bool needsToDecay(const bool mindsBlockByDecay, const int unigramCount,
+            const int bigramCount, const DictionaryHeaderStructurePolicy *const headerPolicy);
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(ForgettingCurveUtils);
@@ -68,6 +88,7 @@
     static const int MIN_VALID_ENCODED_PROBABILITY;
     static const int ENCODED_PROBABILITY_STEP;
     static const float MIN_PROBABILITY_TO_DECAY;
+    static const int DECAY_INTERVAL_SECONDS;
 
     static const ProbabilityTable sProbabilityTable;
 
diff --git a/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java b/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
index b2d31c2..ded8eaa 100644
--- a/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
+++ b/tests/src/com/android/inputmethod/latin/BinaryDictionaryDecayingTests.java
@@ -50,8 +50,8 @@
     }
 
     private void forcePassingShortTime(final BinaryDictionary binaryDictionary) {
-        // Entries having low probability would be suppressed once in 2 GCs.
-        final int count = 2;
+        // Entries having low probability would be suppressed once in 3 GCs.
+        final int count = 3;
         for (int i = 0; i < count; i++) {
             binaryDictionary.getPropertyForTests(SET_NEEDS_TO_DECAY_FOR_TESTING_KEY);
             binaryDictionary.flushWithGC();