0-Based indexes for git log

In git log it uses a 1-based index for the date instead of a 0 based index. So it says "Fri Sep 19 14:23:24 2025 -0400" when it should say "Fri Sep 18 14:23:24 2025 -0400" (or "Friday 2025-8-18 14:23:24 (-4:00.00)"  to get a better format)

Are these date formats locale-specific? In both the US English and France French locales I use commonly, the 19th of September in 2025 _is_ a Friday. Showing 18 would only be confusing.

Showing 19 confuses me because i'm used to 0-based indexes where the 19th is labeld as 18. Showing 18 would not cunfuse most people.

I would need evidence of that. Everyone I interact with agrees to write « 19 » when « 19th » is implied.

As I asked: is this particular to an community? I’m genuinely curious if there are groups or cultures that communicate this way. 

As Peff points out, you can probably make commands display your own personal preference (or a locale should handle this for your community). But I don’t think this is something we can force on other people, because it would be confusing. 

On Tue, Sep 23, 2025 at 05:15:46PM -0400, 𝕍𝕖𝕝𝕠𝕔𝕚𝕗𝕪𝕖𝕣 wrote:

Are you proposing that the first day of September is the 0th? You might be able to do that with locale support and using strftime's %c option, but I'm not sure how powerful locales are (or how one even defines them).

If you just care about the format, check out the --date option in git-log's manpage. Especially the "format:" specifier, which relies on strftime, like:

  git log --date=format:'%A %Y-%m-%d %H:%M:%S (%z)'

-Peff

[sent again because i didn`t reply all

No, i am sugesting that it is still the 1st but it is september 0

On Tue, Sep 23, 2025 at 05:15:46PM -0400, 𝕍𝕖𝕝𝕠𝕔𝕚𝕗𝕪𝕖𝕣 wrote:

Day of month numbers are 1-based.

Nico Williams <nico@cryptonector.com> writes:

Correct.

There are a few things in Git that are 0 based, but not so many.

 * parent numbers are 1-based.  HEAD~1 is the "previous commit", aka
   "first parent".  HEAD~0 is the HEAD itself.

 * merge parent numbers are 2-based (sanity of this statement is
   already questionable).  If HEAD is a merge, HEAD~2 is the
   "(first) side branch that was merged", HEAD~3 is the "(second)
   side brnach that was merged (in an octopus merge), and so on.

 * reflog entries are 1-based.  @{1} is the "previous object pointed
   by the current branch", @{2} is one before that.  @{0} is the
   current branch itself.

 * stash entries are counted 0-based.  "git stash list" shows from
   stash@{0} that is the most recently created stash entry.

No, day of month numbers are 0-based.

HEAD~1 just means HEAD - 1 commit.(AKA "reverse 0-based index")

No, that is just a reverse 0-based index.

That is correct. It's a reverse 0-based index becuase it uses reflog syntax.

HEAD^2, 3, etc., rather? :)

On Wed, Sep 24, 2025 at 01:28:31PM -0400, Ben Knoble wrote:

Probably. I also always regarded this as the nth parent, not the nth merge parent. HEAD^1 returns the first parent even for non-merges, HEAD^2 the second and so on. So I'd claim these are also 1-based.

Patrick

Ben Knoble <ben.knoble@gmail.com> writes:

Thanks for correcting me. Yes. And HEAD^1 is the first parent that is the same as HEAD~1.

I consider day of month to use a 0-based index

On Wed, Sep 24, 2025 at 01:01:30PM -0400, 𝕍𝕖𝕝𝕠𝕔𝕚𝕗𝕪𝕖𝕣 wrote:

The rest of the world does not. You want to be able to interoperate with the rest of the world. So day of month numbers are 1-based. I also wish everything were 0-based, but it's not. That's just life.

I suggest git adds a config option for 0-based date and automaticly uses 0-based date if there is a file at $HOME/use-0-based-index-for-date or $USE-0-BASED-INDEX-FOR-DATE == true

On Wed, Sep 24, 2025 at 10:15 AM 𝕍𝕖𝕝𝕠𝕔𝕚𝕗𝕪𝕖𝕣 <velocifyer@velocifyer.com> wrote:

Git uses strftime from libc for date formatting. strftime[1] doesn't offer a way to format the date as you prefer - what you're asking for appears to be a personal preference, not a standard in any community of the world. I think that your best bet would be to attempt to contribute an option to strftime to render the day of the month from 0-30, but I would be surprised if such a contribution were to be welcomed - as, again, this looks like a preference held by very few. Based on my quick refresher through date.[ch] in the Git codebase, it would be infeasible to add such a flag and custom formatting.

However, Git is open source software, and you're fully welcome to patch your copy of Git to accept such a config (or this ~/some-file, which is not a way Git typically sets configuration) and build it yourself locally.

1: https://www.man7.org/linux/man-pages/man3/strftime.3.html

[resending because i made a typo]

I suggest git adds a config option for 0-based date and automatically uses 0-based date if there is a file at $HOME/.config/use-0-based-index-for-date or $USE-0-BASED-INDEX-FOR-DATE == true