diff --git a/src/PerfPlot.cpp b/src/PerfPlot.cpp
index 260bdc08e..8329812a0 100644
--- a/src/PerfPlot.cpp
+++ b/src/PerfPlot.cpp
@@ -59,7 +59,7 @@ void PerfPlot::plot() {
     boost::shared_ptr<QSettings> settings = GetApplicationSettings();
 
     int  num, tics;
-    tics = 27;
+    tics = 42;
 
     setAxisScale(yLeft, _sc->min(), _sc->max());
     num = xmax - xmin;
@@ -76,6 +76,8 @@ void PerfPlot::plot() {
 	tics  = 7;
     } else if (num < 141) {
 	tics  = 14;
+    } else if (num < 364) {
+	tics  = 27;
     }
     setAxisScale(xBottom, xmin, xmax,tics);
 
diff --git a/src/PerformanceManagerWindow.cpp b/src/PerformanceManagerWindow.cpp
index 7683f21b5..bff695e9e 100644
--- a/src/PerformanceManagerWindow.cpp
+++ b/src/PerformanceManagerWindow.cpp
@@ -21,6 +21,7 @@ PerformanceManagerWindow::PerformanceManagerWindow()
     QLabel *PMSTSLabel = new QLabel(settings->value(GC_STS_ACRONYM,"STS").toString() + ":", this);
     PMSTSValue = new QLineEdit("0");
     PMSTSValue->setReadOnly(true);
+    PMSTSValue->setValidator(new QDoubleValidator(0,500,1,PMSTSValue));
     PMPickerLayout->addWidget(PMSTSLabel);
     PMPickerLayout->addWidget(PMSTSValue);
 
@@ -28,6 +29,7 @@ PerformanceManagerWindow::PerformanceManagerWindow()
 
     PMLTSValue = new QLineEdit("0");
     PMLTSValue->setReadOnly(true);
+    PMLTSValue->setValidator(new QDoubleValidator(0,500,1,PMLTSValue));
     PMPickerLayout->addWidget(PMLTSLabel);
     PMPickerLayout->addWidget(PMLTSValue);
 
@@ -35,6 +37,7 @@ PerformanceManagerWindow::PerformanceManagerWindow()
 
     PMSBValue = new QLineEdit("0");
     PMSBValue->setReadOnly(true);
+    PMSBValue->setValidator(new QDoubleValidator(-500,500,1,PMSBValue));
     PMPickerLayout->addWidget(PMSBLabel);
     PMPickerLayout->addWidget(PMSBValue);
 
@@ -185,19 +188,19 @@ PerformanceManagerWindow::PMpickerMoved(const QPoint &pos)
 
     if (day >= perfplot->min() && day < perfplot->max()) {
 	// set the date string
-	PMDayValue->setText(perfplot->getStartDate().addDays(day).toString());
+	PMDayValue->setText(perfplot->getStartDate().addDays(day).toString("MMM d yyyy"));
 
 
 	sts = perfplot->getSTS(day);
-	QString STSlabel = QString("%1").arg(sts);
+	QString STSlabel = QString("%1").arg(sts,0,'f',1,0);
 	PMSTSValue->setText(STSlabel);
 
 	lts = perfplot->getLTS(day);
-	QString LTSlabel = QString("%1").arg(lts);
+	QString LTSlabel = QString("%1").arg(lts,0,'f',1,0);
 	PMLTSValue->setText(LTSlabel);
 
 	sb = perfplot->getSB(day);
-	QString SBlabel = QString("%1").arg(sb);
+	QString SBlabel = QString("%1").arg(sb,0,'f',1,0);
 	PMSBValue->setText(SBlabel);
     }
 
diff --git a/src/StressCalculator.cpp b/src/StressCalculator.cpp
index 8bf2bc8c6..26bca09e5 100644
--- a/src/StressCalculator.cpp
+++ b/src/StressCalculator.cpp
@@ -27,6 +27,8 @@ StressCalculator::StressCalculator (
     xdays.resize(days+1);
     list.resize(days+1);
 
+    lte = (double)exp(-1.0/longTermDays);
+    ste = (double)exp(-1.0/shortTermDays);
 }
 
 
@@ -211,34 +213,34 @@ void StressCalculator::addRideData(double BS, QDateTime rideDate) {
     // fprintf(stderr,"addRideData (%.2f, %d)\n",BS,daysIndex);
 }
 
+
+/*
+ * calculate stress (in Bike Score units) using
+ * stress = today's BS * (1 - exp(-1/days)) + yesterday's stress * exp(-1/days)
+ * where days is the time period of concern- 7 for STS and 42 for LTS.
+ *
+ * exp(-1/days) for short and long term is calculated when the
+ * class is instantiated.
+ *
+ */
 void StressCalculator::calculate(int daysIndex) {
-    int i;
-    double sum;
+    double lastLTS, lastSTS;
+
     // LTS
-    sum = 0.0;
-    if (daysIndex < longTermDays - 1) {
-	// fake the first N days using the initial value
-	sum = initialLTS * (longTermDays - (daysIndex + 1));
-	i = 0;
-    }
-    else { i =  daysIndex - (longTermDays - 1); }
-    // sum the real values
-    for (; i <= daysIndex; i++)
-	sum += list[i];
-    ltsvalues[daysIndex] = sum / longTermDays;
+    if (daysIndex == 0)
+        lastLTS = initialLTS;
+    else
+        lastLTS = ltsvalues[daysIndex-1];
+
+    ltsvalues[daysIndex] = (list[daysIndex] * (1.0 - lte)) + (lastLTS * lte);
 
     // STS
-    sum = 0.0;
-    if (daysIndex < shortTermDays - 1) {
-	// fake the first N days using the initial value
-	sum = initialSTS * (shortTermDays - (daysIndex + 1));
-	i = 0;
-    }
-    else { i =  daysIndex - (shortTermDays - 1); }
-    // sum the real values
-    for (; i <= daysIndex; i++)
-	sum += list[i];
-    stsvalues[daysIndex] = sum / shortTermDays;
+    if (daysIndex == 0)
+        lastSTS = initialSTS;
+    else
+        lastSTS = stsvalues[daysIndex-1];
+
+    stsvalues[daysIndex] = (list[daysIndex] * (1.0 - ste)) + (lastSTS * ste);
 
     // SB (stress balance)  long term - short term
     sbvalues[daysIndex] =  ltsvalues[daysIndex] - stsvalues[daysIndex] ;
@@ -246,3 +248,4 @@ void StressCalculator::calculate(int daysIndex) {
     // xdays
     xdays[daysIndex] = daysIndex+1;
 }
+
diff --git a/src/StressCalculator.h b/src/StressCalculator.h
index 0f405800e..b933b495f 100644
--- a/src/StressCalculator.h
+++ b/src/StressCalculator.h
@@ -26,6 +26,7 @@ class StressCalculator:public QObject {
 	int longTermDays;
 	double initialSTS;
 	double initialLTS;
+        double ste, lte;
 
 	int lastDaysIndex;