Update the documentation in the wake of https://github.com/bazelbuild/bazel/commit/e52c8418d37e902237c6676d06fcb4cad7fc4766.

RELNOTES: None.
PiperOrigin-RevId: 194240434

site/docs/user-manual.html

diff --git a/site/docs/user-manual.html b/site/docs/user-manual.html
index b3fce7d..27ee793 100644
--- a/site/docs/user-manual.html
+++ b/site/docs/user-manual.html
@@ -2487,8 +2487,8 @@
     <p>Bazel always outputs the following volatile keys:</p>
     <ul>
       <li>
-        <code>BUILD_TIMESTAMP</code>: time of the build in milliseconds since the Unix Epoch (the
-        value of <code>System.currentTimeMillis()</code>)
+        <code>BUILD_TIMESTAMP</code>: time of the build in seconds since the Unix Epoch (the value
+        of <code>System.currentTimeMillis()</code> divided by a thousand)
       </li>
     </ul>
   </li>