diff --git a/util/locale_database/cldr2qtimezone.py b/util/locale_database/cldr2qtimezone.py
index 9c6c9b7f83..537850a3e8 100755
--- a/util/locale_database/cldr2qtimezone.py
+++ b/util/locale_database/cldr2qtimezone.py
@@ -193,7 +193,7 @@ utcIdList = (
     ('UTC-03:00', -10800),
     ('UTC-02:00',  -7200),
     ('UTC-01:00',  -3600),
-    ('UTC-00:00',      0),
+    ('UTC-00:00',      0), # Should recognize, but avoid using (see Note below).
     ('UTC+00:00',      0),
     ('UTC+01:00',   3600),
     ('UTC+02:00',   7200),
@@ -220,6 +220,17 @@ utcIdList = (
 
 ### End of data that may need updates in response to CLDR ###
 
+# Note: -00:00 (without the UTC prefix) was introduced in RFC3339 as a
+# way to indicate that a date-time has been converted to UTC but its
+# use should not be understood to say anything about the local time of
+# the origin of the message using it. However, ISO 8601 has, since
+# 2000, forbidden this as an offset suffix. The more recent compromise
+# is to use Z to convey the meaning RFC3339 gave to -00:00. So the use
+# of -00:00 as offset suffix should be avoided (and, by extension,
+# likewise for UTC-00:00 as a zone ID), but this suffix (and ID)
+# should be recognized when consuming data generated by other sources,
+# for backwards compatibility.
+
 class ByteArrayData:
     def __init__(self):
         self.data = []