* CONTRIBUTING: New file.

* Makefile (COMMON): Add it.
* README, NEWS, Theory, africa, asia, australasia, europe:
* northamerica, southamerica: Mention it.

CONTRIBUTING

@@ -0,0 +1,67 @@
+Contributing to the tz code and data
+
+The time zone database is by no means authoritative: governments
+change timekeeping rules erratically and sometimes with little
+warning, the data entries do not cover all of civil time before
+1970, and undoubtedly errors remain in the code and data.  Feel
+free to fill gaps or fix mistakes, and please email improvements
+to tz@iana.org for use in the future.
+
+To email small changes, please run a POSIX shell command like
+'diff -u old/europe new/europe >myfix.patch', and attach
+myfix.patch to the email.
+
+For more-elaborate changes, please read the Theory file and browse
+the mailing list archives <http://mm.icann.org/pipermail/tz/> for
+examples of patches that tend to work well.  Ideally, additions to
+data should contain commentary citing reliable sources as
+justification.
+
+Please submit changes against either the latest release in
+<ftp://ftp.iana.org/tz/> or the master branch of the experimental
+Git repository.  If you use Git the following workflow may be helpful:
+
+  * Copy the experimental repository.
+
+      git clone git@github.com:eggert/tz.git
+      cd tz
+
+  * Get current with the master branch.
+
+      git checkout master
+      git pull
+
+  * Switch to a new branch for the changes.
+
+      git checkout -b mybranch
+
+  * Edit source files.  Include commentary that justifies the
+    changes by citing reliable sources.
+
+  * Debug the changes, e.g.:
+
+      make check
+      make install
+      ./zdump -v America/Los_Angeles
+
+  * For each separable change, commit it in the new branch, e.g.:
+
+      git add northamerica
+      git commit
+
+    See recent 'git log' output for the commit-message style.
+
+  * Create patch files 0001-*, 0002-*, ...
+
+      git format-patch master
+
+  * After reviewing the patch files, send the patches to tz@iana.org
+    for others to review.
+
+      git send-email master
+
+  * Start anew by getting current with the master branch again.
+
+Please do not create issues or pull requests on Github, as the
+proper procedure for proposing and distributing patches is via
+email as illustrated above.

Makefile

@@ -333,7 +333,7 @@ MANTXTS=	newctime.3.txt newstrftime.3.txt newtzset.3.txt \
 			time2posix.3.txt \
 			tzfile.5.txt tzselect.8.txt zic.8.txt zdump.8.txt \
 			date.1.txt
-COMMON=		Makefile README NEWS
+COMMON=		CONTRIBUTING Makefile README NEWS
 WEB_PAGES=	tz-art.htm tz-link.htm
 DOCS=		Theory $(MANS) date.1 $(MANTXTS) $(WEB_PAGES)
 PRIMARY_YDATA=	africa antarctica asia australasia \

NEWS

@@ -32,6 +32,9 @@ Unreleased, experimental changes
 
   Changes affecting documentation and commentary
 
+    A new file CONTRIBUTING is distributed.  (Thanks to Tim Parenti
+    for suggesting a CONTRIBUTING file.)
+
     tz-link.htm mentions Windows Runtime etc. (thanks to Matt Johnson)
     and HP-UX's tztab.
 

README

@@ -44,11 +44,8 @@ Historical local time information has been included here to:
 	system.
 
 The information in the time zone data files is by no means authoritative;
-the files currently do not even attempt to cover all time stamps before
-1970, and there are undoubtedly errors even for time stamps since 1970.
-If you know that the rules are different from those in a file, by all means
-feel free to change a file (and please send the changed version to
-tz@iana.org for use in the future).  Europeans take note!
+fixes and enhancements are welcome.  Please see the file CONTRIBUTING
+for details.
 
 Thanks to these Time Zone Caballeros who've made major contributions to the
 time conversion package: Keith Bostic; Bob Devine; Paul Eggert; Robert Elz;

Theory

@@ -233,9 +233,9 @@ details of pre-1970 civil timekeeping.
 ----- Accuracy of the tz database -----
 
 The tz database is not authoritative, and it surely has errors.
-Corrections are welcome and encouraged.  Users requiring authoritative
-data should consult national standards bodies and the references cited
-in the database's comments.
+Corrections are welcome and encouraged; see the file CONTRIBUTING.
+Users requiring authoritative data should consult national standards
+bodies and the references cited in the database's comments.
 
 Errors in the tz database arise from many sources:
 

africa

@@ -3,7 +3,8 @@
 
 # This data is by no means authoritative; if you think you know better,
 # go ahead and edit the file (and please send any changes to
-# tz@iana.org for general use in the future).
+# tz@iana.org for general use in the future).  For more, please see
+# the file CONTRIBUTING in the tz distribution.
 
 # From Paul Eggert (2013-02-21):
 #

asia

@@ -3,7 +3,8 @@
 
 # This data is by no means authoritative; if you think you know better,
 # go ahead and edit the file (and please send any changes to
-# tz@iana.org for general use in the future).
+# tz@iana.org for general use in the future).  For more, please see
+# the file CONTRIBUTING in the tz distribution.
 
 # From Paul Eggert (2013-08-11):
 #

australasia

@@ -763,7 +763,8 @@ Zone	Pacific/Wallis	12:15:20 -	LMT	1901
 
 # This data is by no means authoritative; if you think you know better,
 # go ahead and edit the file (and please send any changes to
-# tz@iana.org for general use in the future).
+# tz@iana.org for general use in the future).  For more, please see
+# the file CONTRIBUTING in the tz distribution.
 
 # From Paul Eggert (2013-02-21):
 # A good source for time zone historical data outside the U.S. is

europe

@@ -3,7 +3,8 @@
 
 # This data is by no means authoritative; if you think you know better,
 # go ahead and edit the file (and please send any changes to
-# tz@iana.org for general use in the future).
+# tz@iana.org for general use in the future).  For more, please see
+# the file CONTRIBUTING in the tz distribution.
 
 # From Paul Eggert (2014-05-31):
 # A good source for time zone historical data outside the U.S. is

northamerica

@@ -5,7 +5,8 @@
 
 # This data is by no means authoritative; if you think you know better,
 # go ahead and edit the file (and please send any changes to
-# tz@iana.org for general use in the future).
+# tz@iana.org for general use in the future).  For more, please see
+# the file CONTRIBUTING in the tz distribution.
 
 # From Paul Eggert (1999-03-22):
 # A reliable and entertaining source about time zones is

southamerica

@@ -3,7 +3,8 @@
 
 # This data is by no means authoritative; if you think you know better,
 # go ahead and edit the file (and please send any changes to
-# tz@iana.org for general use in the future).
+# tz@iana.org for general use in the future).  For more, please see
+# the file CONTRIBUTING in the tz distribution.
 
 # From Paul Eggert (2006-03-22):
 # A good source for time zone historical data outside the U.S. is