diff --git a/src/property/pv/timeStamp.h b/src/property/pv/timeStamp.h
index 16e2ac8..2901460 100644
--- a/src/property/pv/timeStamp.h
+++ b/src/property/pv/timeStamp.h
@@ -19,10 +19,10 @@
 
 namespace epics { namespace pvData { 
 
-epicsShareExtern int32 milliSecPerSec;
-epicsShareExtern int32 microSecPerSec;
-epicsShareExtern int32 nanoSecPerSec;
-epicsShareExtern int64 posixEpochAtEpicsEpoch;
+epicsShareExtern const int32 milliSecPerSec;
+epicsShareExtern const int32 microSecPerSec;
+epicsShareExtern const int32 nanoSecPerSec;
+epicsShareExtern const int64 posixEpochAtEpicsEpoch;
 
 /** @brief Methods for manipulating timeStamp.
  * 
diff --git a/src/property/timeStamp.cpp b/src/property/timeStamp.cpp
index 35e7645..7982393 100644
--- a/src/property/timeStamp.cpp
+++ b/src/property/timeStamp.cpp
@@ -21,10 +21,10 @@
 
 namespace epics { namespace pvData { 
 
-int32 milliSecPerSec = 1000;
-int32 microSecPerSec = milliSecPerSec*milliSecPerSec;
-int32 nanoSecPerSec = milliSecPerSec*microSecPerSec;
-int64 posixEpochAtEpicsEpoch = POSIX_TIME_AT_EPICS_EPOCH;
+const int32 milliSecPerSec = 1000;
+const int32 microSecPerSec = 1000000;
+const int32 nanoSecPerSec = 1000000000;
+const int64 posixEpochAtEpicsEpoch = POSIX_TIME_AT_EPICS_EPOCH;
 
 TimeStamp::TimeStamp(int64 secondsPastEpoch,int32 nanoseconds,int32 userTag)
 : secondsPastEpoch(secondsPastEpoch),nanoseconds(nanoseconds),userTag(userTag)