diff --git a/Julian.cpp b/Julian.cpp
index be3917c..4b1e4cd 100755
--- a/Julian.cpp
+++ b/Julian.cpp
@@ -97,7 +97,7 @@ bool Julian::operator==(const Julian &date) const {
 
 bool Julian::operator!=(const Julian &date) const {
 
-    return date_ == date.date_ ? false : true;
+    return !(*this == date);
 }
 
 bool Julian::operator>(const Julian &date) const {
@@ -140,24 +140,34 @@ Julian& Julian::operator=(const double b) {
 /*
  * arithmetic
  */
-Julian Julian::operator+(const Timespan& b) const {
+Julian Julian::operator +(const Timespan& b) const {
 
-    Julian result(*this);
-    result.date_ += b.GetTotalDays();
-    return result;
+    return Julian(*this) += b;
 }
 
 Julian Julian::operator-(const Timespan& b) const {
 
-    Julian result(*this);
-    result.date_ -= b.GetTotalDays();
-    return result;
+    return Julian(*this) -= b;
 }
 
 Timespan Julian::operator-(const Julian& b) const {
 
-    Timespan result(date_ - b.date_);
-    return result;
+    return Timespan(date_ - b.date_);
+}
+
+/*
+ * compound assignment
+ */
+Julian & Julian::operator +=(const Timespan& b) {
+
+    date_ += b;
+    return (*this);
+}
+
+Julian & Julian::operator -=(const Timespan& b) {
+
+    date_ -= b;
+    return (*this);
 }
 
 std::ostream & operator<<(std::ostream& stream, const Julian& julian) {
@@ -165,13 +175,13 @@ std::ostream & operator<<(std::ostream& stream, const Julian& julian) {
     std::stringstream out;
     struct Julian::DateTimeComponents datetime;
     julian.ToGregorian(&datetime);
-    out << std::right << std::fixed << std::setprecision(3) << std::setfill('0');
+    out << std::right << std::fixed << std::setprecision(6) << std::setfill('0');
     out << std::setw(4) << datetime.years << "-";
     out << std::setw(2) << datetime.months << "-";
     out << std::setw(2) << datetime.days << " ";
     out << std::setw(2) << datetime.hours << ":";
     out << std::setw(2) << datetime.minutes << ":";
-    out << std::setw(6) << datetime.seconds << " UTC";
+    out << std::setw(9) << datetime.seconds << " UTC";
     stream << out.str();
     return stream;
 }
diff --git a/Julian.h b/Julian.h
index aa7b6e7..c936358 100755
--- a/Julian.h
+++ b/Julian.h
@@ -18,9 +18,7 @@ public:
     ~Julian() {
     };
 
-    /*
-     * comparison operators
-     */
+    // comparison operators
     bool operator==(const Julian &date) const;
     bool operator!=(const Julian &date) const;
     bool operator>(const Julian &date) const;
@@ -28,16 +26,16 @@ 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;
+    // assignment
+    Julian& operator =(const Julian& b);
+    Julian& operator =(const double b);
+    // arithmetic
+    Julian operator +(const Timespan& b) const;
+    Julian operator -(const Timespan& b) const;
+    Timespan operator -(const Julian& b) const;
+    // compound assignment
+    Julian & operator +=(const Timespan& b);
+    Julian & operator -=(const Timespan& b);
 
     friend std::ostream & operator<<(std::ostream& stream, const Julian& julian);
 
diff --git a/PassPredict.cpp b/PassPredict.cpp
index e332cd3..e4abe4d 100755
--- a/PassPredict.cpp
+++ b/PassPredict.cpp
@@ -4,6 +4,8 @@
 #include <cmath>
 #include <iostream>
 
+const int kPASS_TIME_STEP = 180; // time step in seconds, when searching for aos/los
+
 double FindMaxElevation(const CoordGeodetic& user_geo, SGP4& sgp4, const Julian& aos, const Julian& los) {
 
     Observer obs(user_geo);
@@ -61,7 +63,7 @@ double FindMaxElevation(const CoordGeodetic& user_geo, SGP4& sgp4, const Julian&
              * reset elevation
              */
             max_elevation = -99.9;
-            
+
         } else {
             /*
              * found max elevation
@@ -120,7 +122,7 @@ Julian FindCrossingPoint(const CoordGeodetic& user_geo, SGP4& sgp4, const Julian
         /*
          * when two times are within a second, stop
          */
-        if (((time2.GetDate() - time1.GetDate()) * kSECONDS_PER_DAY) < 1.0) {
+        if (((time2.GetDate() - time1.GetDate()) * kSECONDS_PER_DAY) < 0.5) {
             searching = false;
         }
 
@@ -136,6 +138,9 @@ void AOSLOS(const CoordGeodetic& user_geo, SGP4& sgp4, const Julian& start_time,
     Observer obs(user_geo);
     Eci eci;
 
+    Timespan time_step;
+    time_step.AddMinutes(kPASS_TIME_STEP);
+
     bool first_run = true;
     Julian previous_time = start_time;
 
@@ -147,6 +152,7 @@ void AOSLOS(const CoordGeodetic& user_geo, SGP4& sgp4, const Julian& start_time,
     Julian current_time = start_time;
     while (current_time < end_time) {
 
+        // find position
         sgp4.FindPosition(&eci, current_time);
         CoordTopographic topo = obs.GetLookAngle(eci);
 
@@ -189,7 +195,7 @@ void AOSLOS(const CoordGeodetic& user_geo, SGP4& sgp4, const Julian& start_time,
         first_run = false;
         previous_time = current_time;
 
-        current_time.AddMin(1.0);
+        current_time += time_step;
         if (current_time > end_time)
             current_time = end_time;
     };
diff --git a/Timespan.cpp b/Timespan.cpp
index 55ebc17..261b46e 100755
--- a/Timespan.cpp
+++ b/Timespan.cpp
@@ -6,7 +6,7 @@ Timespan::Timespan()
 : time_span_(0.0) {
 }
 
-Timespan::Timespan(const double b){
+Timespan::Timespan(const double b) {
 
     time_span_ = b;
 }
@@ -146,3 +146,15 @@ bool Timespan::operator <=(const Timespan & b) const {
     else
         return false;
 }
+
+double& operator +=(double& a, const Timespan& b) {
+
+    a += b.time_span_;
+    return a;
+}
+
+double& operator -=(double& a, const Timespan& b) {
+
+    a -= b.time_span_;
+    return a;
+}
\ No newline at end of file
diff --git a/Timespan.h b/Timespan.h
index e8ccff6..b1e68dc 100755
--- a/Timespan.h
+++ b/Timespan.h
@@ -38,6 +38,9 @@ public:
     bool operator>=(const Timespan& b) const;
     bool operator<=(const Timespan& b) const;
 
+    friend double& operator +=(double& a, const Timespan& b);
+    friend double& operator -=(double& a, const Timespan& b);
+
 private:
     /*
      * stores value in minutes