diff --git a/src/d_main.cpp b/src/d_main.cpp
index f94d158b5..75605b2e7 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -941,7 +941,7 @@ void D_Display ()
 	else
 	{
 		// wipe update
-		unsigned int wipestart, nowtime, diff;
+		uint64_t wipestart, nowtime, diff;
 		bool done;
 
 		GSnd->SetSfxPaused(true, 1);
diff --git a/src/d_net.cpp b/src/d_net.cpp
index ba1262025..e8711bda5 100644
--- a/src/d_net.cpp
+++ b/src/d_net.cpp
@@ -113,9 +113,9 @@ bool	 		remoteresend[MAXNETNODES];				// set when local needs tics
 int 			resendto[MAXNETNODES];					// set when remote needs tics
 int 			resendcount[MAXNETNODES];
 
-unsigned int	lastrecvtime[MAXPLAYERS];				// [RH] Used for pings
-unsigned int	currrecvtime[MAXPLAYERS];
-unsigned int	lastglobalrecvtime;						// Identify the last time a packet was received.
+uint64_t		lastrecvtime[MAXPLAYERS];				// [RH] Used for pings
+uint64_t		currrecvtime[MAXPLAYERS];
+uint64_t		lastglobalrecvtime;						// Identify the last time a packet was received.
 bool			hadlate;
 int				netdelay[MAXNETNODES][BACKUPTICS];		// Used for storing network delay times.
 int				lastaverage;
diff --git a/src/dobject.cpp b/src/dobject.cpp
index 9046d7337..df8bb1acb 100644
--- a/src/dobject.cpp
+++ b/src/dobject.cpp
@@ -615,7 +615,7 @@ void DObject::CheckIfSerialized () const
 
 DEFINE_ACTION_FUNCTION(DObject, MSTime)
 {
-	ACTION_RETURN_INT(I_msTime());
+	ACTION_RETURN_INT((uint32_t)I_msTime());
 }
 
 void *DObject::ScriptVar(FName field, PType *type)
diff --git a/src/g_level.h b/src/g_level.h
index 2df5af946..e7305e9da 100644
--- a/src/g_level.h
+++ b/src/g_level.h
@@ -362,7 +362,7 @@ struct level_info_t
 	int			outsidefogdensity;
 	int			skyfog;
 	float		pixelstretch;
-	
+
 	// Redirection: If any player is carrying the specified item, then
 	// you go to the RedirectMap instead of this one.
 	FName		RedirectType;
diff --git a/src/g_levellocals.h b/src/g_levellocals.h
index b7f4f9aa3..505d797b6 100644
--- a/src/g_levellocals.h
+++ b/src/g_levellocals.h
@@ -67,6 +67,8 @@ struct FLevelLocals
 	FString		F1Pic;
 	EMapType	maptype;
 
+	uint64_t	ShaderStartTime = 0;	// tell the shader system when we started the level (forces a timer restart)
+
 	TArray<vertex_t> vertexes;
 	TArray<sector_t> sectors;
 	TArray<line_t*> linebuffer;	// contains the line lists for the sectors.
diff --git a/src/gl/models/gl_models.cpp b/src/gl/models/gl_models.cpp
index 541a4c36c..963518a99 100644
--- a/src/gl/models/gl_models.cpp
+++ b/src/gl/models/gl_models.cpp
@@ -53,9 +53,9 @@
 #include "gl/renderer/gl_renderstate.h"
 #include "gl/shaders/gl_shader.h"
 
-static inline float GetTimeFloat()
+static inline double GetTimeFloat()
 {
-	return (float)screen->FrameTime * (float)TICRATE / 1000.0f;
+	return (double)screen->FrameTime * (double)TICRATE / 1000.;
 }
 
 CVAR(Bool, gl_interpolate_model_frames, true, CVAR_ARCHIVE)
@@ -890,7 +890,7 @@ void gl_RenderFrameModels( const FSpriteModelFrame *smf,
 			// [BB] In case the tic counter is frozen we have to leave ticFraction at zero.
 			if ( ConsoleState == c_up && menuactive != MENU_On && !(level.flags2 & LEVEL2_FROZEN) )
 			{
-				float time = GetTimeFloat();
+				double time = GetTimeFloat();
 				ticFraction = (time - static_cast<int>(time));
 			}
 			inter = static_cast<double>(curState->Tics - curTics - ticFraction)/static_cast<double>(curState->Tics);
@@ -999,8 +999,8 @@ void gl_RenderModel(GLSprite * spr)
 
 	if( smf->flags & MDL_ROTATING )
 	{
-		const float time = smf->rotationSpeed*GetTimeFloat()/200.f;
-		rotateOffset = float((time - xs_FloorToInt(time)) *360.f );
+		const double time = smf->rotationSpeed*GetTimeFloat()/200.;
+		rotateOffset = double((time - xs_FloorToInt(time)) *360. );
 	}
 
 	// Added MDL_USEACTORPITCH and MDL_USEACTORROLL flags processing.
diff --git a/src/gl/renderer/gl_renderstate.cpp b/src/gl/renderer/gl_renderstate.cpp
index 1427e2350..c37ccbb99 100644
--- a/src/gl/renderer/gl_renderstate.cpp
+++ b/src/gl/renderer/gl_renderstate.cpp
@@ -37,6 +37,7 @@
 #include "gl/renderer/gl_colormap.h"
 #include "gl/dynlights//gl_lightbuffer.h"
 #include "gl/renderer/gl_renderbuffers.h"
+#include "g_levellocals.h"
 
 void gl_SetTextureMode(int type);
 
@@ -118,6 +119,12 @@ void FRenderState::Reset()
 
 bool FRenderState::ApplyShader()
 {
+	static uint64_t firstFrame = 0;
+	// if firstFrame is not yet initialized, initialize it to current time
+	// if we're going to overflow a float (after ~4.6 hours, or 24 bits), re-init to regain precision
+	if ((firstFrame == 0) || (screen->FrameTime - firstFrame >= 1<<24) || level.ShaderStartTime >= firstFrame)
+		firstFrame = screen->FrameTime;
+
 	static const float nulvec[] = { 0.f, 0.f, 0.f, 0.f };
 	if (mSpecialEffect > EFF_NONE)
 	{
@@ -161,7 +168,7 @@ bool FRenderState::ApplyShader()
 	activeShader->muInterpolationFactor.Set(mInterpolationFactor);
 	activeShader->muClipHeight.Set(mClipHeight);
 	activeShader->muClipHeightDirection.Set(mClipHeightDirection);
-	activeShader->muTimer.Set(screen->FrameTime * mShaderTimer / 1000.f);
+	activeShader->muTimer.Set((double)(screen->FrameTime - firstFrame) * mShaderTimer / 1000.f);
 	activeShader->muAlphaThreshold.Set(mAlphaThreshold);
 	activeShader->muLightIndex.Set(mLightIndex);	// will always be -1 for now
 	activeShader->muClipSplit.Set(mClipSplit);
diff --git a/src/gl/scene/gl_scene.cpp b/src/gl/scene/gl_scene.cpp
index 92d378521..329ac6484 100644
--- a/src/gl/scene/gl_scene.cpp
+++ b/src/gl/scene/gl_scene.cpp
@@ -800,8 +800,8 @@ sector_t * GLSceneDrawer::RenderViewpoint (AActor * camera, GL_IRECT * bounds, f
 	GLRenderer->mAngles.Roll.Degrees = r_viewpoint.Angles.Roll.Degrees;
 
 	// Scroll the sky
-	GLRenderer->mSky1Pos = (float)fmod(screen->FrameTime * level.skyspeed1, 1024.f) * 90.f/256.f;
-	GLRenderer->mSky2Pos = (float)fmod(screen->FrameTime * level.skyspeed2, 1024.f) * 90.f/256.f;
+	GLRenderer->mSky1Pos = (double)fmod(screen->FrameTime * level.skyspeed1, 1024.f) * 90./256.;
+	GLRenderer->mSky2Pos = (double)fmod(screen->FrameTime * level.skyspeed2, 1024.f) * 90./256.;
 
 
 
diff --git a/src/gl/utility/gl_clock.cpp b/src/gl/utility/gl_clock.cpp
index 8ad3b1cc8..df96fb6b8 100644
--- a/src/gl/utility/gl_clock.cpp
+++ b/src/gl/utility/gl_clock.cpp
@@ -187,8 +187,8 @@ static void AppendLightStats(FString &out)
 ADD_STAT(rendertimes)
 {
 	static FString buff;
-	static int lasttime=0;
-	int t=I_msTime();
+	static int64_t lasttime=0;
+	int64_t t=I_msTime();
 	if (t-lasttime>1000) 
 	{
 		buff.Truncate(0);
@@ -217,7 +217,7 @@ void AppendMissingTextureStats(FString &out);
 
 static int printstats;
 static bool switchfps;
-static unsigned int waitstart;
+static uint64_t waitstart;
 EXTERN_CVAR(Bool, vid_fps)
 
 void CheckBench()
diff --git a/src/i_time.cpp b/src/i_time.cpp
index 050bb1ebc..4be0a8b82 100644
--- a/src/i_time.cpp
+++ b/src/i_time.cpp
@@ -60,9 +60,9 @@ static uint64_t MSToNS(unsigned int ms)
 	return static_cast<uint64_t>(ms) * 1'000'000;
 }
 
-static uint32_t NSToMS(uint64_t ns)
+static uint64_t NSToMS(uint64_t ns)
 {
-	return static_cast<uint32_t>(ns / 1'000'000);
+	return static_cast<uint64_t>(ns / 1'000'000);
 }
 
 static int NSToTic(uint64_t ns)
@@ -125,7 +125,7 @@ uint64_t I_nsTime()
 	return GetClockTimeNS();
 }
 
-unsigned int I_msTime()
+uint64_t I_msTime()
 {
 	return NSToMS(I_nsTime());
 }
diff --git a/src/i_time.h b/src/i_time.h
index 160596969..33907ded2 100644
--- a/src/i_time.h
+++ b/src/i_time.h
@@ -20,7 +20,7 @@ int I_WaitForTic(int);
 void I_FreezeTime(bool frozen);
 
 // [RH] Returns millisecond-accurate time
-unsigned int I_msTime();
+uint64_t I_msTime();
 
 // Nanosecond-accurate time
 uint64_t I_nsTime();
diff --git a/src/p_glnodes.cpp b/src/p_glnodes.cpp
index bac573565..e1510145e 100644
--- a/src/p_glnodes.cpp
+++ b/src/p_glnodes.cpp
@@ -955,7 +955,7 @@ bool P_CheckNodes(MapData * map, bool rebuilt, int buildtime)
 		if (!loaded)
 		{
 			// none found - we have to build new ones!
-			unsigned int startTime, endTime;
+			uint64_t startTime, endTime;
 
 			startTime = I_msTime ();
 			TArray<FNodeBuilder::FPolyStart> polyspots, anchors;
@@ -973,7 +973,7 @@ bool P_CheckNodes(MapData * map, bool rebuilt, int buildtime)
 			builder.Extract (level);
 			endTime = I_msTime ();
 			DPrintf (DMSG_NOTIFY, "BSP generation took %.3f sec (%u segs)\n", (endTime - startTime) * 0.001, level.segs.Size());
-			buildtime = endTime - startTime;
+			buildtime = (int32_t)(endTime - startTime);
 		}
 	}
 
diff --git a/src/p_setup.cpp b/src/p_setup.cpp
index 02522d3df..dfa7ecb26 100644
--- a/src/p_setup.cpp
+++ b/src/p_setup.cpp
@@ -3627,6 +3627,8 @@ void P_SetupLevel (const char *lumpname, int position)
 	bool buildmap;
 	const int *oldvertextable = NULL;
 
+	level.ShaderStartTime = I_msTime(); // indicate to the shader system that the level just started
+
 	// This is motivated as follows:
 
 	bool RequireGLNodes = Renderer->RequireGLNodes() || am_textured;
@@ -3931,7 +3933,7 @@ void P_SetupLevel (const char *lumpname, int position)
 	}
 	else reloop = true;
 
-	unsigned int startTime=0, endTime=0;
+	uint64_t startTime=0, endTime=0;
 
 	bool BuildGLNodes;
 	if (ForceNodeBuild)
@@ -3988,7 +3990,7 @@ void P_SetupLevel (const char *lumpname, int position)
 		// If the original nodes being loaded are not GL nodes they will be kept around for
 		// use in P_PointInSubsector to avoid problems with maps that depend on the specific
 		// nodes they were built with (P:AR E1M3 is a good example for a map where this is the case.)
-		reloop |= P_CheckNodes(map, BuildGLNodes, endTime - startTime);
+		reloop |= P_CheckNodes(map, BuildGLNodes, (uint32_t)(endTime - startTime));
 		hasglnodes = true;
 	}
 	else
diff --git a/src/r_sky.cpp b/src/r_sky.cpp
index eb31e2064..cc84f9fbb 100644
--- a/src/r_sky.cpp
+++ b/src/r_sky.cpp
@@ -165,7 +165,7 @@ void R_InitSkyMap ()
 //
 //==========================================================================
 
-void R_UpdateSky (uint32_t mstime)
+void R_UpdateSky (uint64_t mstime)
 {
 	// Scroll the sky
 	double ms = (double)mstime * FRACUNIT;
diff --git a/src/r_sky.h b/src/r_sky.h
index 39ac77f27..e186ad3ae 100644
--- a/src/r_sky.h
+++ b/src/r_sky.h
@@ -44,6 +44,6 @@ extern int		freelookviewheight;
 
 // Called whenever the sky changes.
 void R_InitSkyMap		();
-void R_UpdateSky (uint32_t mstime);
+void R_UpdateSky (uint64_t mstime);
 
 #endif //__R_SKY_H__
diff --git a/src/textures/animations.cpp b/src/textures/animations.cpp
index 7b2aab98b..a9fa4c1bf 100644
--- a/src/textures/animations.cpp
+++ b/src/textures/animations.cpp
@@ -876,7 +876,7 @@ FDoorAnimation *FTextureManager::FindAnimatedDoor (FTextureID picnum)
 //
 //==========================================================================
 
-void FAnimDef::SetSwitchTime (uint32_t mstime)
+void FAnimDef::SetSwitchTime (uint64_t mstime)
 {
 	int speedframe = bDiscrete ? CurFrame : 0;
 
@@ -917,7 +917,7 @@ void FTextureManager::SetTranslation (FTextureID fromtexnum, FTextureID totexnum
 //
 //==========================================================================
 
-void FTextureManager::UpdateAnimations (uint32_t mstime)
+void FTextureManager::UpdateAnimations (uint64_t mstime)
 {
 	for (unsigned int j = 0; j < mAnimations.Size(); ++j)
 	{
diff --git a/src/textures/textures.h b/src/textures/textures.h
index 96bd8d3ca..539d38c43 100644
--- a/src/textures/textures.h
+++ b/src/textures/textures.h
@@ -90,7 +90,7 @@ struct FAnimDef
 	uint16_t	CurFrame;
 	uint8_t	AnimType;
 	bool	bDiscrete;			// taken out of AnimType to have better control
-	uint32_t	SwitchTime;			// Time to advance to next frame
+	uint64_t	SwitchTime;			// Time to advance to next frame
 	struct FAnimFrame
 	{
 		uint32_t	SpeedMin;		// Speeds are in ms, not tics
@@ -106,7 +106,7 @@ struct FAnimDef
 		ANIM_Random
 	};
 
-	void SetSwitchTime (uint32_t mstime);
+	void SetSwitchTime (uint64_t mstime);
 };
 
 struct FSwitchDef
@@ -505,7 +505,7 @@ public:
 
 	int NumTextures () const { return (int)Textures.Size(); }
 
-	void UpdateAnimations (uint32_t mstime);
+	void UpdateAnimations (uint64_t mstime);
 	int GuesstimateNumTextures ();
 
 	FSwitchDef *FindSwitch (FTextureID texture);
@@ -604,8 +604,8 @@ public:
 	void SetSpeed(float fac) { Speed = fac; }
 	FTexture *GetRedirect(bool wantwarped);
 
-	uint32_t GenTime;
-	uint32_t GenTimeBgra;
+	uint64_t GenTime;
+	uint64_t GenTimeBgra;
 	float Speed;
 	int WidthOffsetMultiplier, HeightOffsetMultiplier;  // [mxd]
 protected:
@@ -613,7 +613,7 @@ protected:
 	uint8_t *Pixels;
 	Span **Spans;
 
-	virtual void MakeTexture (uint32_t time);
+	virtual void MakeTexture (uint64_t time);
 	int NextPo2 (int v); // [mxd]
 	void SetupMultipliers (int width, int height); // [mxd]
 };
diff --git a/src/textures/warpbuffer.h b/src/textures/warpbuffer.h
index 668c40aeb..62b0db13d 100644
--- a/src/textures/warpbuffer.h
+++ b/src/textures/warpbuffer.h
@@ -35,7 +35,7 @@
 #include "textures/textures.h"
 
 template<class TYPE> 
-void WarpBuffer(TYPE *Pixels, const TYPE *source, int width, int height, int xmul, int ymul, unsigned time, float Speed, int warptype)
+void WarpBuffer(TYPE *Pixels, const TYPE *source, int width, int height, int xmul, int ymul, uint64_t time, float Speed, int warptype)
 {
 	int ymask = height - 1;
 	int x, y;
diff --git a/src/textures/warptexture.cpp b/src/textures/warptexture.cpp
index 43a215a2b..2e073c186 100644
--- a/src/textures/warptexture.cpp
+++ b/src/textures/warptexture.cpp
@@ -86,7 +86,7 @@ bool FWarpTexture::CheckModified ()
 
 const uint8_t *FWarpTexture::GetPixels ()
 {
-	uint32_t time = screen->FrameTime;
+	uint64_t time = screen->FrameTime;
 
 	if (Pixels == NULL || time != GenTime)
 	{
@@ -97,7 +97,7 @@ const uint8_t *FWarpTexture::GetPixels ()
 
 const uint32_t *FWarpTexture::GetPixelsBgra()
 {
-	uint32_t time = screen->FrameTime;
+	uint64_t time = screen->FrameTime;
 	if (Pixels == NULL || time != GenTime)
 		MakeTexture(time);
 
@@ -119,7 +119,7 @@ const uint32_t *FWarpTexture::GetPixelsBgra()
 
 const uint8_t *FWarpTexture::GetColumn (unsigned int column, const Span **spans_out)
 {
-	uint32_t time =screen->FrameTime;
+	uint64_t time =screen->FrameTime;
 
 	if (Pixels == NULL || time != GenTime)
 	{
@@ -148,7 +148,7 @@ const uint8_t *FWarpTexture::GetColumn (unsigned int column, const Span **spans_
 }
 
 
-void FWarpTexture::MakeTexture(uint32_t time)
+void FWarpTexture::MakeTexture(uint64_t time)
 {
 	const uint8_t *otherpix = SourcePic->GetPixels();
 
diff --git a/src/v_video.cpp b/src/v_video.cpp
index 5f774a648..01ae8b428 100644
--- a/src/v_video.cpp
+++ b/src/v_video.cpp
@@ -870,8 +870,8 @@ void DFrameBuffer::DrawRateStuff ()
 	// Draws frame time and cumulative fps
 	if (vid_fps)
 	{
-		uint32_t ms = screen->FrameTime;
-		uint32_t howlong = ms - LastMS;
+		uint64_t ms = screen->FrameTime;
+		uint64_t howlong = ms - LastMS;
 		if ((signed)howlong >= 0)
 		{
 			char fpsbuff[40];
@@ -888,7 +888,7 @@ void DFrameBuffer::DrawRateStuff ()
 				DTA_VirtualHeight, screen->GetHeight() / textScale,
 				DTA_KeepRatio, true, TAG_DONE);
 
-			uint32_t thisSec = ms/1000;
+			uint32_t thisSec = (uint32_t)(ms/1000);
 			if (LastSec < thisSec)
 			{
 				LastCount = FrameCount / (thisSec - LastSec);
@@ -903,8 +903,8 @@ void DFrameBuffer::DrawRateStuff ()
 	// draws little dots on the bottom of the screen
 	if (ticker)
 	{
-		int i = I_GetTime();
-		int tics = i - LastTic;
+		int64_t i = I_GetTime();
+		int64_t tics = i - LastTic;
 		uint8_t *buffer = GetBuffer();
 
 		LastTic = i;
@@ -931,6 +931,7 @@ void DFrameBuffer::DrawRateStuff ()
 		}
 		else
 		{
+			int i;
 			for (i = 0; i < tics*2; i += 2)		Clear(i, Height-1, i+1, Height, 255, 0);
 			for ( ; i < 20*2; i += 2)			Clear(i, Height-1, i+1, Height, 0, 0);
 		}
diff --git a/src/v_video.h b/src/v_video.h
index 5934a3706..1cbf565af 100644
--- a/src/v_video.h
+++ b/src/v_video.h
@@ -442,7 +442,7 @@ public:
 
 	virtual void ScaleCoordsFromWindow(int16_t &x, int16_t &y) {}
 
-	uint32_t GetLastFPS() const { return LastCount; }
+	uint64_t GetLastFPS() const { return LastCount; }
 
 #ifdef _WIN32
 	virtual void PaletteChanged () = 0;
@@ -453,7 +453,7 @@ public:
 	// The original size of the framebuffer as selected in the video menu.
 	int VideoWidth = 0;
 	int VideoHeight = 0;
-	uint32_t FrameTime = 0;
+	uint64_t FrameTime = 0;
 
 protected:
 	void DrawRateStuff ();
@@ -463,7 +463,7 @@ protected:
 	DFrameBuffer () {}
 
 private:
-	uint32_t LastMS, LastSec, FrameCount, LastCount, LastTic;
+	uint64_t LastMS, LastSec, FrameCount, LastCount, LastTic;
 	bool isIn2D = false;
 };