diff --git a/lib/process_shared/posix/semaphore.rb b/lib/process_shared/posix/semaphore.rb
index 11f9e9d..a1ef3a5 100644
--- a/lib/process_shared/posix/semaphore.rb
+++ b/lib/process_shared/posix/semaphore.rb
@@ -83,10 +83,6 @@ module ProcessShared
         sem_wait(@sem)
       end
 
-      NS_PER_S = 1e9
-      US_PER_NS = 1000
-      TV_NSEC_MAX = (NS_PER_S - 1)
-
       # Decrement the value of the semaphore if it can be done
       # immediately (i.e. if it was non-zero).  Otherwise, wait up to
       # +timeout+ seconds until another process increments via {#post}.
@@ -100,24 +96,9 @@ module ProcessShared
       def try_wait(timeout = nil)
         if timeout
           now = TimeVal.new
-          abs_timeout = TimeSpec.new
-
           LibC.gettimeofday(now, nil)
-
-          abs_timeout[:tv_sec] = now[:tv_sec];
-          abs_timeout[:tv_nsec] = now[:tv_usec] * US_PER_NS
-
-          # add timeout in seconds to abs_timeout; careful with rounding
-          sec = timeout.floor
-          nsec = ((timeout - sec) * NS_PER_S).floor
-
-          abs_timeout[:tv_sec] += sec
-          abs_timeout[:tv_nsec] += nsec
-          while abs_timeout[:tv_nsec] > TV_NSEC_MAX
-            abs_timeout[:tv_sec] += 1
-            abs_timeout[:tv_nsec] -= NS_PER_S
-          end
-
+          abs_timeout = now.to_time_spec
+          abs_timeout.add_seconds!(timeout)
           sem_timedwait(@sem, abs_timeout)
         else
           sem_trywait(@sem)
diff --git a/lib/process_shared/posix/time_spec.rb b/lib/process_shared/posix/time_spec.rb
index 36e36c6..246bf1f 100644
--- a/lib/process_shared/posix/time_spec.rb
+++ b/lib/process_shared/posix/time_spec.rb
@@ -1,8 +1,11 @@
 require 'ffi'
+require 'process_shared/time_spec'
 
 module ProcessShared
   module Posix
     class TimeSpec < FFI::Struct
+      include ProcessShared::TimeSpec
+
       layout(:tv_sec, :time_t,
              :tv_nsec, :long)
     end
diff --git a/lib/process_shared/posix/time_val.rb b/lib/process_shared/posix/time_val.rb
index edac9df..cc856d4 100644
--- a/lib/process_shared/posix/time_val.rb
+++ b/lib/process_shared/posix/time_val.rb
@@ -1,10 +1,23 @@
 require 'ffi'
 
+require 'process_shared/posix/time_spec'
+
 module ProcessShared
   module Posix
     class TimeVal < FFI::Struct
+      US_PER_NS = 1000
+
       layout(:tv_sec, :time_t,
              :tv_usec, :suseconds_t)
+
+      def to_time_spec
+        ts = TimeSpec.new
+
+        ts[:tv_sec] = self[:tv_sec];
+        ts[:tv_nsec] = self[:tv_usec] * US_PER_NS
+
+        ts
+      end
     end
   end
 end
diff --git a/lib/process_shared/time_spec.rb b/lib/process_shared/time_spec.rb
new file mode 100644
index 0000000..1bca648
--- /dev/null
+++ b/lib/process_shared/time_spec.rb
@@ -0,0 +1,22 @@
+module ProcessShared
+  module TimeSpec
+    NS_PER_S = 1e9
+    US_PER_NS = 1000
+    TV_NSEC_MAX = (NS_PER_S - 1)
+
+    # Assuming self responds to setting the value of [:tv_sec] and
+    # [:tv_nsec], add +secs+ to the time spec.
+    def add_seconds!(float_sec)
+      # add timeout in seconds to abs_timeout; careful with rounding
+      sec = float_sec.floor
+      nsec = ((float_sec - sec) * NS_PER_S).floor
+
+      self[:tv_sec] += sec
+      self[:tv_nsec] += nsec
+      while self[:tv_nsec] > TV_NSEC_MAX
+        self[:tv_sec] += 1
+        self[:tv_nsec] -= NS_PER_S
+      end
+    end
+  end
+end