diff --git a/src/d_main.cpp b/src/d_main.cpp
index 9d8055b0d..6247a5339 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -781,7 +781,7 @@ void D_Display ()
 
 
 	{
-		screen->FrameTime = I_msTime();
+		screen->FrameTime = I_msTimeFS();
 		TexMan.UpdateAnimations(screen->FrameTime);
 		R_UpdateSky(screen->FrameTime);
 		switch (gamestate)
diff --git a/src/i_time.cpp b/src/i_time.cpp
index 0511a79f0..bd8a3817a 100644
--- a/src/i_time.cpp
+++ b/src/i_time.cpp
@@ -164,6 +164,11 @@ uint64_t I_msTime()
 	return NSToMS(I_nsTime());
 }
 
+uint64_t I_msTimeFS() // from "start"
+{
+	return NSToMS(I_nsTime() - FirstFrameStartTime);
+}
+
 int I_GetTime()
 {
 	return NSToTic(CurrentFrameStartTime - FirstFrameStartTime);
diff --git a/src/i_time.h b/src/i_time.h
index 33907ded2..63c4586f1 100644
--- a/src/i_time.h
+++ b/src/i_time.h
@@ -22,5 +22,8 @@ void I_FreezeTime(bool frozen);
 // [RH] Returns millisecond-accurate time
 uint64_t I_msTime();
 
+// [SP] Returns millisecond-accurate time from start
+uint64_t I_msTimeFS();
+
 // Nanosecond-accurate time
 uint64_t I_nsTime();