Clarify that deadline_timer uses a UTC-based clock by default.

asio/include/asio/deadline_timer.hpp

diff --git a/asio/include/asio/deadline_timer.hpp b/asio/include/asio/deadline_timer.hpp
index 0ea3737..eefd406 100644
--- a/asio/include/asio/deadline_timer.hpp
+++ b/asio/include/asio/deadline_timer.hpp
@@ -27,7 +27,7 @@
 
 namespace asio {
 
-/// Typedef for the typical usage of timer.
+/// Typedef for the typical usage of timer. Uses a UTC clock.
 typedef basic_deadline_timer<boost::posix_time::ptime> deadline_timer;
 
 } // namespace asio

asio/src/doc/reference.qbk

diff --git a/asio/src/doc/reference.qbk b/asio/src/doc/reference.qbk
index a2e721d..6802656 100644
--- a/asio/src/doc/reference.qbk
+++ b/asio/src/doc/reference.qbk
@@ -35354,7 +35354,7 @@
 [section:deadline_timer deadline_timer]
 
 [indexterm1 deadline_timer] 
-Typedef for the typical usage of timer. 
+Typedef for the typical usage of timer. Uses a UTC clock. 
 
 
   typedef basic_deadline_timer< boost::posix_time::ptime > deadline_timer;