diff --git a/Timestamp-Synchronization.md b/Timestamp-Synchronization.md
index f444264..b917694 100644
--- a/Timestamp-Synchronization.md
+++ b/Timestamp-Synchronization.md
@@ -217,3 +217,10 @@ sudo ptp4l -i eth0 -l 6 -m
 
 When a sync packet appears on the network, it indicates that the master clock of ptp4l is successfully turned on.
 
+Use the following command, PTP Hardware Clock is synchronized to system clock.
+
+`phc2sys` usage: http://manpages.ubuntu.com/manpages/cosmic/man8/phc2sys.8.html
+
+```bash
+sudo phc2sys -c eth0 -s CLOCK_REALTIME -O 0
+```
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