diff --git a/signal/signal.can b/signal/signal.can
index 004160f..c732e32 100644
--- a/signal/signal.can
+++ b/signal/signal.can
@@ -99,7 +99,7 @@ let signal = {
 	-- For example, every ubiquitousse module with a "update" function will bind it to the "update" signal in the registry;
 	-- you can then call this signal on each game update to update every ubiquitousse module easily.
 	-- Provided signals:
-	-- * update, should be called on every game update
+	-- * update(dt), should be called on every game update
 	-- * draw, should be called on every game draw
 	-- * for LÖVE, there are callbacks for every LÖVE callback function that need to be called on their corresponding LÖVE callback
 	-- @impl mixed
diff --git a/timer/backend/ctrulua.lua b/timer/backend/ctrulua.lua
deleted file mode 100644
index 05143c1..0000000
--- a/timer/backend/ctrulua.lua
+++ /dev/null
@@ -1,6 +0,0 @@
-local timer = require((...):match("^(.-%.)backend").."timer")
-local ctr = require("ctr")
-
-timer.get = ctr.time
-
-return timer
\ No newline at end of file
diff --git a/timer/backend/love.lua b/timer/backend/love.lua
deleted file mode 100644
index ea57669..0000000
--- a/timer/backend/love.lua
+++ /dev/null
@@ -1,7 +0,0 @@
-local timer = require((...):match("^(.-%.)backend").."timer")
-
-timer.get = function()
-	return love.timer.getTime() * 1000
-end
-
-return timer
\ No newline at end of file
diff --git a/timer/init.lua b/timer/init.lua
index 2b758c4..0b454dc 100644
--- a/timer/init.lua
+++ b/timer/init.lua
@@ -1,14 +1 @@
-local time
-
-local p = ...
-if love then
-	time = require(p..".backend.love")
-elseif package.loaded["ctr"] then
-	time = require(p..".backend.ctrulua")
-elseif package.loaded["libretro"] then
-	error("NYI")
-else
-	error("no backend for ubiquitousse.timer")
-end
-
-return time
+return require((...)..".timer")
diff --git a/timer/timer.lua b/timer/timer.lua
index a17ef44..10ea0a1 100644
--- a/timer/timer.lua
+++ b/timer/timer.lua
@@ -1,5 +1,4 @@
 --- ubiquitousse.timer
--- Depends on a backend.
 -- Optional dependencies: ubiquitousse.signal (to bind to update signal in signal.event)
 local loaded, signal = pcall(require, (...):match("^(.-)timer").."signal")
 if not loaded then signal = nil end
@@ -29,15 +28,9 @@ end
 local registry_mt = {
 	--- Update all the TimedFunctions calls.
 	-- Should be called at every game update; called by ubiquitousse.update.
-	-- @tparam[opt=calculate here] number dt the delta-time (time spent since last time the function was called) (miliseconds)
+	-- @tparam number dt the delta-time (time spent since last time the function was called) (miliseconds)
 	-- @impl ubiquitousse
 	update = function(self, dt)
-		local currentTime = timer.get()
-
-		if not dt then
-			dt = currentTime - self.lastTime
-			self.lastTime = currentTime
-		end
 		self.dt = dt
 
 		local done = {} -- functions done running
@@ -47,36 +40,50 @@ local registry_mt = {
 			if t and all(t.initWhen, true) then
 				t.initWhen = {}
 				local co = t.coroutine
-				t.after = t.after - dt
-				if t.forceStart or (t.after <= 0 and all(t.startWhen, true)) then
+				-- skip
+				dt = self.dt
+				if t.skip then dt = dt + t.skip end
+				-- start
+				if t.after then t.after = t.after - dt end
+				if t.forceStart or ((not t.after or t.after <= 0) and all(t.startWhen, true)) then
+					local startLag = 0
+					if t.after then
+						startLag = -t.after
+					elseif t.skip then
+						startLag = t.skip
+					end
+					t.after, t.skip = nil, nil
 					t.startWhen = {}
 					d[func] = false -- niling here cause the next pair iteration to error
 					table.insert(done, func)
 					if not co then
 						co = coroutine.create(func)
 						t.coroutine = co
-						t.started = currentTime
 						if t.times > 0 then t.times = t.times - 1 end
-						for _, f in ipairs(t.onStart) do f(t.object) end
+						for _, f in ipairs(t.onStart) do f(t.object, startLag) end
 					end
+					-- update
 					assert(coroutine.resume(co, function(delay)
-						t.after = delay or 0
+						t.after = delay - startLag
 						d[func] = t
 						coroutine.yield()
 					end, dt))
-					for _, f in ipairs(t.onUpdate) do f(t.object) end
+					for _, f in ipairs(t.onUpdate) do f(t.object, startLag) end
+					if t.during then t.during = t.during - startLag - dt end
+					-- stopping / repeat
 					if all(t.stopWhen, false) then t.forceStop = true end
 					if t.forceStop or coroutine.status(co) == "dead" then
 						if t.forceStop
-							or (t.during >= 0 and t.started + t.during < currentTime)
+							or (t.during and t.during <= 0)
 							or (t.times == 0)
 							or (not all(t.repeatWhile, true))
-							or (t.every == -1 and t.times == -1 and t.during == -1 and #t.repeatWhile == 0) -- no repeat
+							or (t.every == nil and t.times == -1 and t.during == nil and #t.repeatWhile == 0) -- no repeat
 						then
-							for _, f in ipairs(t.onEnd) do f(t.object) end
+							local endLag = t.during and -t.during or 0
+							for _, f in ipairs(t.onEnd) do f(t.object, endLag) end
 						else
 							if t.times > 0 then t.times = t.times - 1 end
-							t.after = t.every
+							if t.every then t.after = t.every - startLag end
 							t.coroutine = coroutine.create(func)
 							d[func] = t
 						end
@@ -95,6 +102,7 @@ local registry_mt = {
 	--- Schedule a function to run.
 	-- The function will receive as first parameter the wait(time) function, which will pause the function execution for time miliseconds.
 	-- As a second parameter, the function will receive the delta time (dt).
+	-- As a third parameter, the function will receive the lag time (difference between the time when the function was run and when it should have been run).
 	-- @tparam[opt] function func the function to schedule
 	-- @treturn TimedFunction the object
 	-- @impl ubiquitousse
@@ -107,12 +115,11 @@ local registry_mt = {
 		self.delayed[func] = {
 			object = nil,
 			coroutine = nil,
-			started = 0,
 
-			after = -1,
-			every = -1,
+			after = nil,
+			every = nil,
 			times = -1,
-			during = -1,
+			during = nil,
 
 			initWhen = {},
 			startWhen = {},
@@ -121,6 +128,7 @@ local registry_mt = {
 
 			forceStart = false,
 			forceStop = false,
+			skip = nil,
 
 			onStart = {},
 			onUpdate = {},
@@ -132,21 +140,25 @@ local registry_mt = {
 		r = {
 			--- Timed conditions ---
 			--- Wait time milliseconds before running the function.
+			-- Specify no time to remove condition.
 			after = function(_, time)
 				t.after = time
 				return r
 			end,
 			--- Run the function every time millisecond.
+			-- Specify no time to remove condition.
 			every = function(_, time)
 				t.every = time
 				return r
 			end,
 			--- The function will not execute more than count times.
+			-- Specify no time to remove condition.
 			times = function(_, count)
-				t.times = count
+				t.times = count or -1
 				return r
 			end,
 			--- The TimedFunction will be active for a time duration.
+			-- Specify no time to remove condition.
 			during = function(_, time)
 				t.during = time
 				return r
@@ -191,32 +203,40 @@ local registry_mt = {
 				t.forceStop = true
 				return r
 			end,
+			--- Skip some amount of time.
+			skip = function(_, time)
+				t.skip = (t.skip or 0) + time
+			end,
 
 			--- Callbacks functions ---
-			--- Will execute func(self) when the function execution start.
+			--- Will execute func(self, lag) when the function execution start.
 			onStart = function(_, func)
 				table.insert(t.onStart, func)
 				return r
 			end,
-			--- Will execute func(self) each frame the main function is run.
+			--- Will execute func(self, lag) each frame the main function is run.
 			onUpdate = function(_, func)
 				table.insert(t.onUpdate, func)
 				return r
 			end,
-			--- Will execute func(self) when the function execution end.
+			--- Will execute func(self, lag) when the function execution end.
 			onEnd = function(_, func)
 				table.insert(t.onEnd, func)
 				return r
 			end,
 
 			--- Chaining ---
-			--- Creates another TimedFunction which will be initialized when the current one ends.
+			--- Creates another TimedFunction which will be initialized immediately when the current one ends.
 			-- Returns the new TimedFunction.
 			chain = function(_, func)
 				local done = false
-				r:onEnd(function() done = true end)
-				return self:run(func)
+				local fn = self:run(func)
 					:initWhen(function() return done end)
+				r:onEnd(function(self, lag)
+					done = true
+					fn:skip(lag)
+				end)
+				return fn
 			end
 		}
 		t.object = r
@@ -284,9 +304,13 @@ local registry_mt = {
 			end
 
 			local done = false
-			r:onEnd(function() done = true end)
-			return self:tween(duration_, tbl_, to_, method_)
+			local fn = self:tween(duration_, tbl_, to_, method_)
 				:initWhen(function() return done end)
+			r:onEnd(function(self, lag)
+				done = true
+				fn:skip(lag)
+			end)
+			return fn
 		end
 
 		return r
@@ -314,20 +338,11 @@ timer = {
 			-- This table is for internal use and shouldn't be used from an external script.
 			delayed = {},
 
-			-- Used to calculate the deltatime
-			lastTime = timer.get(),
-
 			--- Time since last timer update (miliseconds).
 			dt = 0
 		}, registry_mt)
 	end,
 
-	--- Returns the number of miliseconds elapsed since some point in time.
-	-- This point is fixed but undetermined, so this function should only be used to calculate durations.
-	-- Should at least have millisecond-precision, but can be more precise if available.
-	-- @impl backend
-	get = function() end,
-
 	--- Time since last update (miliseconds).
 	-- @impl ubiquitousse
 	dt = 0,
@@ -335,7 +350,6 @@ timer = {
 	--- Global TimerRegistry.
 	-- @impl ubiquitousse
 	delayed = {},
-	lastTime = 0,
 	update = function(...) -- If ubiquitousse.signal is available, will be bound to the "update" signal in signal.event.
 		return registry_mt.update(timer, ...)
 	end,