--- a/date.rst	Sat Dec 04 16:21:48 2010 +0200
+++ b/date.rst	Sat Dec 04 16:51:29 2010 +0200
@@ -54,3 +54,25 @@
 ** Debian Lenny.
 
   $ sudo dpkg-reconfigure tzdata
+
+* About timestamp.
+
+  http://en.wikipedia.org/wiki/Timestamp
+  http://en.wikipedia.org/wiki/Unix_time
+  http://en.wikipedia.org/wiki/Leap_second
+
+** Get timestamp.
+
+Current timestamp:
+
+  $ date +%s
+
+Timestamp for specific date/time:
+
+  $ date -d '2010-12-11' +%s
+  $ date -d '2010-12-11 23:59:59' +%s
+
+** Convert unix timestamp to date.
+
+  $ date -d '1970-01-01 + 1234567890 seconds'
+