diff --git a/README.md b/README.md
index b22e0a4..e153a6f 100644
--- a/README.md
+++ b/README.md
@@ -300,6 +300,46 @@ julia> print_timer()
 
 The default timer object can be retrieved with `TimerOutputs.get_defaulttimer()`.
 
+## Measuring time consumed outside `@timeit` blocks
+
+Often, operations that we do not consider time consuming turn out to be relevant.
+However, adding additional timming blocks just to time initializations and other
+less important calls is annoying.
+
+The `TimerOutputs.complement!` function can be used to modify a timer and add
+values for complement of timed sections. For instance:
+
+```julia
+to = TimerOutput()
+
+@timeit to "section1" sleep(0.02)
+@timeit to "section2" begin
+    @timeit to "section2.1" sleep(0.1)
+    sleep(0.01)
+end
+
+TimerOutputs.complement!(to)
+```
+
+We can print the result:
+
+```julia
+julia> print_timer(to)
+ ───────────────────────────────────────────────────────────────────────
+                                Time                   Allocations
+                        ──────────────────────   ───────────────────────
+    Tot / % measured:        144ms / 100%            6.11KiB / 22.0%
+
+ Section        ncalls     time   %tot     avg     alloc   %tot      avg
+ ───────────────────────────────────────────────────────────────────────
+ section2            1    120ms  83.6%   120ms   1.17KiB  87.2%  1.17KiB
+   section2.1        1    106ms  73.9%   106ms      176B  12.8%     176B
+   ~section2~        1   13.9ms  9.69%  13.9ms   1.00KiB  74.4%  1.00KiB
+ section1            1   23.4ms  16.4%  23.4ms      176B  12.8%     176B
+ ───────────────────────────────────────────────────────────────────────
+```
+
+In order to complement the default timer simply call `TimerOuputs.complement!()`.
 
 ## Overhead
 
diff --git a/src/TimerOutput.jl b/src/TimerOutput.jl
index 324bb86..c9855e5 100644
--- a/src/TimerOutput.jl
+++ b/src/TimerOutput.jl
@@ -308,7 +308,6 @@ function _flatten!(to::TimerOutput, inner_timers::Dict{String,TimerOutput})
     end
 end
 
-
 enable_timer!(to::TimerOutput=DEFAULT_TIMER) = to.enabled = true
 disable_timer!(to::TimerOutput=DEFAULT_TIMER) = to.enabled = false
 
@@ -321,6 +320,28 @@ end
 # Default function throws an error for the benefit of the user
 notimeit_expr(args...) = throw(ArgumentError("invalid macro usage for @notimeit, use as @notimeit [to] codeblock"))
 
+complement!() = complement!(DEFAULT_TIMER)
+function complement!(to::TimerOutput)
+    if length(to.inner_timers) == 0
+        return nothing
+    end
+    tot_time = to.accumulated_data.time
+    tot_allocs = to.accumulated_data.allocs
+    for timer in values(to.inner_timers)
+        tot_time -= timer.accumulated_data.time
+        tot_allocs -= timer.accumulated_data.allocs
+        complement!(timer)
+    end
+    tot_time = max(tot_time, 0)
+    tot_allocs = max(tot_allocs, 0)
+    if !(to.name in ["root", "Flattened"])
+        name = string("~", to.name, "~")
+        timer = TimerOutput(to.start_data, TimeData(max(1,to.accumulated_data.ncalls), tot_time, tot_allocs), Dict{String,TimerOutput}(), TimerOutput[], name, false, true, (tot_time, tot_allocs), to.name, to)
+        to.inner_timers[name] = timer
+    end
+    return to
+end
+
 # If @notimeit was called without a TimerOutput instance, use default timer
 notimeit_expr(ex::Expr) = notimeit_expr(:($(TimerOutputs.DEFAULT_TIMER)), ex)
 
diff --git a/test/runtests.jl b/test/runtests.jl
index 1b23837..73b91b6 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -305,6 +305,17 @@ baz(1, 2.0)
 @test "sleep" in keys(to_debug.inner_timers["baz"].inner_timers)
 TimerOutputs.disable_debug_timings(@__MODULE__)
 
+to = TimerOutput()
+@timeit to "section1" sleep(0.02)
+@timeit to "section2" begin
+    @timeit to "section2.1" sleep(0.1)
+    sleep(0.01)
+end
+TimerOutputs.complement!(to)
+
+tom = flatten(to)
+@test ncalls(tom["~section2~"]) == 1
+
 end # testset
 
 struct Simulation