diff --git a/SGDP4.cpp b/SGDP4.cpp
index 8faef95..3a50b9b 100644
--- a/SGDP4.cpp
+++ b/SGDP4.cpp
@@ -218,16 +218,19 @@ void SGDP4::Initialize(const double& theta2, const double& betao2, const double&
     first_run_ = false;
 }
 
-void SGDP4::FindPosition(Eci& eci, double tsince) {
-
-    Julian tsince_epoch = Epoch();
-    tsince_epoch.AddMin(tsince);
-    double actual_tsince = tsince_epoch.SpanMin(Epoch());
+void SGDP4::FindPosition(Eci& eci, double tsince) const {
 
     if (i_use_deep_space_)
-        FindPositionSDP4(eci, actual_tsince);
+        FindPositionSDP4(eci, tsince);
     else
-        FindPositionSGP4(eci, actual_tsince);
+        FindPositionSGP4(eci, tsince);
+}
+
+void SGDP4::FindPosition(Eci& eci, const Julian& date) const {
+
+    const double tsince = date.SpanMin(Epoch());
+
+    FindPosition(eci, tsince);
 }
 
 void SGDP4::FindPositionSDP4(Eci& eci, double tsince) const {
diff --git a/SGDP4.h b/SGDP4.h
index 0ce5163..2a0faef 100644
--- a/SGDP4.h
+++ b/SGDP4.h
@@ -10,7 +10,8 @@ public:
     virtual ~SGDP4(void);
 
     void SetTle(const Tle& tle);
-    void FindPosition(Eci& eci, double tsince);
+    void FindPosition(Eci& eci, double tsince) const;
+    void FindPosition(Eci& eci, const Julian& date) const;
 
 private:
     void Initialize(const double& theta2, const double& betao2, const double& betao, const double& eosq);