1 # Contributing to the tz code and data 2 3 Please do not create issues or pull requests on GitHub, as the 4 proper procedure for proposing and distributing patches is via 5 email as described below. 6 7 The time zone database is by no means authoritative: governments 8 change timekeeping rules erratically and sometimes with little 9 warning, the data entries do not cover all of civil time before 10 1970, and undoubtedly errors remain in the code and data. Feel 11 free to fill gaps or fix mistakes, and please email improvements 12 to <tz (a] iana.org> for use in the future. In your email, please give 13 reliable sources that reviewers can check. The mailing list and its 14 archives are public, so please do not send confidential information. 15 16 ## Contributing technical changes 17 18 To email small changes, please run a POSIX shell command like 19 diff -u old/europe new/europe >myfix.patch, and attach 20 myfix.patch to the email. 21 22 For more-elaborate or possibly controversial changes, 23 such as renaming, adding or removing zones, please read 24 Theory and pragmatics of the tz code and data 25 <https://www.iana.org/time-zones/repository/theory.html>. 26 It is also good to browse the mailing list archives 27 <https://lists.iana.org/hyperkitty/list/tz@iana.org/> 28 for examples of patches that tend to work well. 29 Changes should contain commentary citing reliable sources. 30 Citations should use https: URLs if available. 31 32 For changes that fix sensitive security-related bugs, please see the 33 distributions SECURITY file. 34 35 Please submit changes against either the latest release 36 <https://www.iana.org/time-zones> or the main branch of the development 37 repository. The latter is preferred. 38 39 ## Sample Git workflow for developing contributions 40 41 If you use Git the following workflow may be helpful: 42 43 * Copy the development repository. 44 45 git clone https://github.com/eggert/tz.git 46 cd tz 47 48 * Get current with the main branch. 49 50 git checkout main 51 git pull 52 53 * Switch to a new branch for the changes. Choose a different 54 branch name for each change set. 55 56 git checkout -b mybranch 57 58 * Sleuth by using git blame. For example, when fixing data for 59 Africa/Sao_Tome, if the command git blame africa outputs a line 60 2951fa3b (Paul Eggert 2018-01-08 09:03:13 -0800 1068) Zone 61 Africa/Sao_Tome 0:26:56 - LMT 1884, commit 2951fa3b should 62 provide some justification for the Zone Africa/Sao_Tome line. 63 64 * Edit source files. Include commentary that justifies the 65 changes by citing reliable sources. 66 67 * Debug the changes locally, e.g.: 68 69 make TOPDIR=$PWD/tz clean check install 70 ./zdump -v America/Los_Angeles 71 72 Although builds assume only basic POSIX, they use extra features 73 if available. make check accesses validator.w3.org unless you 74 lack curl or use make CURL=:. If you have the latest GCC, 75 make CFLAGS='$(GCC_DEBUG_FLAGS)' does extra checking. 76 77 * For each separable change, commit it in the new branch, e.g.: 78 79 git add northamerica 80 git commit 81 82 See recent git log output for the commit-message style. 83 84 * Create patch files 0001-..., 0002-..., ... 85 86 git format-patch main 87 88 * Check that the patch files and your email setup contain only 89 information that you want to make public. 90 91 * After reviewing the patch files, send the patches to <tz (a] iana.org> 92 for others to review. 93 94 git send-email main 95 96 For an archived example of such an email, see 97 [PROPOSED] Fix off-by-1 error for Jamaica and T&C before 1913 98 <https://mm.icann.org/pipermail/tz/2018-February/026122.html>. 99 100 * Start anew by getting current with the main branch again 101 (the second step above). 102 103 ----- 104 105 This file is in the public domain. 106
Indexes created Wed Jun 17 00:25:26 UTC 2026