diff --git a/Doc/library/time.rst b/Doc/library/time.rst
--- a/Doc/library/time.rst
+++ b/Doc/library/time.rst
@@ -22,6 +22,12 @@
   year, at 0 hours, the "time since the epoch" is zero.  For Unix, the epoch is
   1970.  To find out what the epoch is, look at ``gmtime(0)``.
 
+   .. note::
+
+      Currently, many functions in the stdlib assume that :func:`.time` returns
+      the calendar time in POSIX encoding in particular that
+      ``gmtime(0).tm_year`` is 1970.
+
 .. index:: single: Year 2038
 
 * The functions in this module may not handle dates and times before the epoch or
@@ -688,4 +694,3 @@
    year (%y rather than %Y), but practice moved to 4-digit years long before the
    year 2000.  After that, :rfc:`822` became obsolete and the 4-digit year has
    been first recommended by :rfc:`1123` and then mandated by :rfc:`2822`.
-