diff --git a/Julian.h b/Julian.h
index ff332f9..aa7b6e7 100755
--- a/Julian.h
+++ b/Julian.h
@@ -28,16 +28,26 @@ public:
     bool operator>=(const Julian &date) const;
     bool operator<=(const Julian &date) const;
 
+    // asign Julian
     Julian & operator=(const Julian& b);
+    // assign double
     Julian & operator=(const double b);
+    // add Timespan
     Julian operator+(const Timespan& b) const;
+    // subtract Timespan
     Julian operator-(const Timespan& b) const;
-
+    // subtracting two Julians produces a Timespan
     Timespan operator-(const Julian& b) const;
 
     friend std::ostream & operator<<(std::ostream& stream, const Julian& julian);
 
     struct DateTimeComponents {
+
+        DateTimeComponents()
+        : years(0), months(0), days(0),
+        hours(0), minutes(0), seconds(0.0) {
+        }
+
         int years;
         int months;
         int days;
@@ -84,22 +94,6 @@ public:
         date_ += (sec / kSECONDS_PER_DAY);
     }
 
-    double SpanDay(const Julian& b) const {
-        return date_ - b.date_;
-    }
-
-    double SpanHour(const Julian& b) const {
-        return SpanDay(b) * kHOURS_PER_DAY;
-    }
-
-    double SpanMin(const Julian& b) const {
-        return SpanDay(b) * kMINUTES_PER_DAY;
-    }
-
-    double SpanSec(const Julian& b) const {
-        return SpanDay(b) * kSECONDS_PER_DAY;
-    }
-
     static bool IsLeapYear(int y) {
         return (y % 4 == 0 && y % 100 != 0) || (y % 400 == 0);
     }
diff --git a/Makefile b/Makefile
index 4b65fcb..25f5f77 100755
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 CC=g++
 AR=ar
-CFLAGS=-c -Wall -O2 -pedantic -ansi
+CFLAGS=-c -Wall -g -pedantic -ansi
 LDFLAGS=
 
 SOURCES=CoordGeodetic.cpp \
diff --git a/PassPredict.cpp b/PassPredict.cpp
index e61132e..e332cd3 100755
--- a/PassPredict.cpp
+++ b/PassPredict.cpp
@@ -91,7 +91,7 @@ Julian FindCrossingPoint(const CoordGeodetic& user_geo, SGP4& sgp4, const Julian
     Julian time1 = initial_time1;
     Julian time2 = initial_time2;
 
-    Julian middle_time = time1 + (time2.GetDate() - time1.GetDate()) / 2.0;
+    Julian middle_time = time1 + (time2 - time1) / 2.0;
 
     while (searching && loop_count < 25) {
 
@@ -124,7 +124,7 @@ Julian FindCrossingPoint(const CoordGeodetic& user_geo, SGP4& sgp4, const Julian
             searching = false;
         }
 
-        middle_time = time1 + (time2.GetDate() - time1.GetDate()) / 2.0;
+        middle_time = time1 + (time2 - time1) / 2.0;
         loop_count++;
     };
 
diff --git a/SGP4.cpp b/SGP4.cpp
index 4933358..dfc879a 100755
--- a/SGP4.cpp
+++ b/SGP4.cpp
@@ -236,9 +236,9 @@ void SGP4::FindPosition(Eci* eci, double tsince) const {
 
 void SGP4::FindPosition(Eci* eci, const Julian& date) const {
 
-    const double tsince = date.SpanMin(Epoch());
+    Timespan diff = date - Epoch();
 
-    FindPosition(eci, tsince);
+    FindPosition(eci, diff.GetTotalMinutes());
 }
 
 void SGP4::FindPositionSDP4(Eci* eci, double tsince) const {
@@ -581,8 +581,9 @@ void SGP4::CalculateFinalPositionVelocity(Eci* eci, const double& tsince, const
     const double zdot = (rdotk * uz + rfdotk * vz) * kXKMPER / 60.0;
     Vector velocity(xdot, ydot, zdot);
 
-    Julian julian = Epoch();
-    julian.AddMin(tsince);
+    Timespan diff;
+    diff.AddMinutes(tsince);
+    Julian julian = Epoch() + diff;
     (*eci) = Eci(julian, position, velocity);
 }
 
diff --git a/Timespan.cpp b/Timespan.cpp
old mode 100644
new mode 100755
index 7bb812d..55ebc17
--- a/Timespan.cpp
+++ b/Timespan.cpp
@@ -2,24 +2,38 @@
 
 #include "Globals.h"
 
-Timespan::Timespan(void) {
+Timespan::Timespan()
+: time_span_(0.0) {
 }
 
-/*
- * time_span is days and fraction of a day
- */
-Timespan::Timespan(const double time_span) {
-    time_span_ = time_span;
+Timespan::Timespan(const double b){
+
+    time_span_ = b;
 }
 
 Timespan::Timespan(const Timespan& b) {
-
     time_span_ = b.time_span_;
 }
 
 Timespan::~Timespan(void) {
 }
 
+void Timespan::AddDays(const double days) {
+    time_span_ += days;
+}
+
+void Timespan::AddHours(const double hours) {
+    time_span_ += (hours / kHOURS_PER_DAY);
+}
+
+void Timespan::AddMinutes(const double minutes) {
+    time_span_ += (minutes / kMINUTES_PER_DAY);
+}
+
+void Timespan::AddSeconds(const double seconds) {
+    time_span_ += (seconds / kSECONDS_PER_DAY);
+}
+
 double Timespan::GetTotalDays() const {
     return time_span_;
 }
@@ -40,49 +54,52 @@ Timespan& Timespan::operator =(const Timespan& b) {
 
     if (this != &b) {
         time_span_ = b.time_span_;
-
     }
     return (*this);
 }
 
 Timespan Timespan::operator +(const Timespan& b) const {
 
-    Timespan result(*this);
-    result.time_span_ += b.GetTotalDays();
-    return result;
+    return Timespan(*this) += b;
 }
 
 Timespan Timespan::operator -(const Timespan& b) const {
 
-    Timespan result(*this);
-    result.time_span_ -= b.GetTotalDays();
-    return result;
+    return Timespan(*this) -= b;
 }
 
-const Timespan & Timespan::operator+=(const Timespan& b) {
+Timespan Timespan::operator/(const double b) const {
+
+    return Timespan(*this) /= b;
+}
+
+Timespan Timespan::operator*(const double b) const {
+
+    return Timespan(*this) *= b;
+}
+
+Timespan & Timespan::operator+=(const Timespan& b) {
 
     time_span_ += b.time_span_;
     return (*this);
 }
 
-const Timespan & Timespan::operator-=(const Timespan& b) {
+Timespan & Timespan::operator-=(const Timespan& b) {
 
     time_span_ -= b.time_span_;
     return (*this);
 }
 
-Timespan Timespan::operator +() const {
+Timespan & Timespan::operator/=(const double b) {
 
-    Timespan result(*this);
-    result.time_span_ = +result.time_span_;
-    return result;
+    time_span_ /= b;
+    return (*this);
 }
 
-Timespan Timespan::operator -() const {
+Timespan & Timespan::operator*=(const double b) {
 
-    Timespan result(*this);
-    result.time_span_ = -result.time_span_;
-    return result;
+    time_span_ *= b;
+    return (*this);
 }
 
 bool Timespan::operator ==(const Timespan& b) const {
@@ -95,10 +112,7 @@ bool Timespan::operator ==(const Timespan& b) const {
 
 bool Timespan::operator !=(const Timespan& b) const {
 
-    if (time_span_ == b.time_span_)
-        return false;
-    else
-        return true;
+    return !(*this == b);
 }
 
 bool Timespan::operator>(const Timespan& b) const {
diff --git a/Timespan.h b/Timespan.h
old mode 100644
new mode 100755
index 6f7136f..e8ccff6
--- a/Timespan.h
+++ b/Timespan.h
@@ -3,26 +3,34 @@
 
 class Timespan {
 public:
-    Timespan(void);
-    Timespan(const double time_span);
+    Timespan();
+    Timespan(const double b);
     Timespan(const Timespan& b);
     virtual ~Timespan(void);
 
+    void AddDays(const double days);
+    void AddHours(const double hours);
+    void AddMinutes(const double minutes);
+    void AddSeconds(const double seconds);
+
     double GetTotalDays() const;
     double GetTotalHours() const;
     double GetTotalMinutes() const;
     double GetTotalSeconds() const;
 
-    /*
-     * overloaded operators
-     */
+    // assignment
     Timespan & operator=(const Timespan& b);
+    // arithmetic
     Timespan operator+(const Timespan& b) const;
     Timespan operator-(const Timespan& b) const;
-    Timespan operator+() const;
-    Timespan operator-() const;
-    const Timespan & operator+=(const Timespan& b);
-    const Timespan & operator-=(const Timespan& b);
+    Timespan operator/(const double b) const;
+    Timespan operator*(const double b) const;
+    // compound arithmetic
+    Timespan & operator+=(const Timespan& b);
+    Timespan & operator-=(const Timespan& b);
+    Timespan & operator/=(const double b);
+    Timespan & operator*=(const double b);
+    // comparison
     bool operator==(const Timespan& b) const;
     bool operator!=(const Timespan& b) const;
     bool operator>(const Timespan& b) const;