[tz] [PROPOSED 1/3] Document that -00 means local time is unspecified

[Paul Eggert]

* tzfile.5, zic.8: Document longstanding practice in time zone
abbreviations.  This better matches draft RFC 8536bis.
---
 tzfile.5 | 4 +++-
 zic.8    | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/tzfile.5 b/tzfile.5
index 74564cb..e2f11b4 100644
--- a/tzfile.5
+++ b/tzfile.5
@@ -118,7 +118,9 @@ and
 serves as an index into the array of time zone abbreviation bytes
 that follow the
 .B ttinfo
-structure(s) in the file.
+entries in the file; if the designated string is "\*-00", the
+.B ttinfo
+entry is a placeholder indicating that local time is unspecified.
 The
 .B tt_utoff
 value is never equal to \-2**31, to let 32-bit clients negate it without
diff --git a/zic.8 b/zic.8
index 3727922..89fc827 100644
--- a/zic.8
+++ b/zic.8
@@ -559,6 +559,9 @@ alphanumeric ASCII characters,
 .q "+"
 and
 .q "\*-".
+By convention, the time zone abbreviation
+.q "\*-00"
+is a placeholder that means local time is unspecified.
 .TP
 .B UNTIL
 The time at which the UT offset or the rule(s) change for a location.
-- 
2.30.2