diff --git a/man/os-release.xml b/man/os-release.xml
index fd98be5b7a3..c5a53ae7eb5 100644
--- a/man/os-release.xml
+++ b/man/os-release.xml
@@ -355,9 +355,12 @@
The date at which support for this version of the OS ends. (What exactly "lack of
support" means varies between vendors, but generally users should assume that updates, including
- security fixes, will not be provided.) The value is a date in the format
- YYYY-MM-DD, and specifies the last day on which support is
- provided.
+ security fixes, will not be provided.) The value is a date in the ISO 8601 format
+ YYYY-MM-DD, and specifies the first day on which support is
+ not provided.
+
+ For example, SUPPORT_END=2001-01-01 means that the system was supported
+ until the end of the last day of the previous millenium.