User's Local Time Does Not Consider Changes in Their Region's Zone Offset #3049

Likely impossible, this is all the information we have, no daylight savings info:

From 299ed7c1f3e4711867b4d0f1c030da474d846fc4 Mon Sep 17 00:00:00 2001
Date: Fri, 1 May 2020 03:07:39 -0400
Subject: [PATCH] Add support for Metafield and Product

and https://api.github.com/repos/ScreenStaring/recharge-api/commits/299ed7c1f3e4711867b4d0f1c030da474d846fc4

At some point we used to use geolocate the user with their bio information, but that's less accurate (made up or missing) and required API calls to a 3rd party (Google)

Hi, this would't work:

const timeAdjustment = new Date().getTimezoneOffset() - new Date(commitTime).getTimezoneOffset()

?

As MDN says:

const date1 = new Date('August 19, 1975 23:15:30 GMT+07:00');
const date2 = new Date('August 19, 1975 23:15:30 GMT-02:00');

console.log(date1.getTimezoneOffset());
// expected output: your local timezone offset in minutes
// (eg -120). NOT the timezone offset of the date object.

We want to display the user's time in my local timezone which may differ if it's currently daylight savings time. Given this (in Chrome):

> new Date() 
Sat May 02 2020 13:54:50 GMT-0400 (Eastern Daylight Time)
> new Date().getTimezoneOffset()
240
> new Date('August 19, 1975 23:15:30 GMT+07:00').getTimezoneOffset()
240
// Time change is in effect during this time
> new Date('December 24, 1975 23:15:30 GMT+07:00').getTimezoneOffset()
300
> new Date('December 24, 1975 23:15:30 GMT+07:00').getTimezoneOffset() - new Date().getTimezoneOffset()
60

Seems like it would work, no?

Can you do a test?

1. Run this on a repo you just committed to:

git log -1

2. Google Current time

What are your values?

I get

commit a351ce6baf0d83d41892e079f9c1eb05c6d3940c (HEAD -> master)
Author: Federico Brigante <opensource@bfred.it>
Date:   Sat May 2 20:16:42 2020 +0200

    Avoid duplicate event handlers in `toggle-everything-with-alt`

9:20 PM
Saturday, May 2, 2020 (GMT+2)
Time in Province of Lecce 

It appears that GIT saves daylight savings in the timestamp since my timezone should be GMT+1 but we're currently in Daylight Savings Time, so the log’s +0200 is correct and should work correctly.

~/code/ruby/file_types >git --no-pager log -1
commit 32306b5e5e8151f3f3691a20bfd686a232925588
Author: sshaw <skye.shaw@gmail.com>
Date:   Sat May 2 17:13:25 2020 -0400

    Initial commit

<img width="685" alt="Screen Shot 2020-05-02 at 5 31 54 PM" src="https://user-images.githubusercontent.com/17570/80892820-05011d00-8c9b-11ea-815f-60d64b98fc38.png">

-0400 appears to be EDT, so yeah git is giving us the right time and we're showing the right time as well.

This is what Refined GitHub shows for you:

<img width="348" alt="" src="https://user-images.githubusercontent.com/1402241/80893252-01888880-8cd1-11ea-95a2-07a3f484dc7e.png">

Looks correct. Where's the bug? My guess is that your colleague’s timezone is either old (we have a 10-day cache) or git stored the wrong timezone somehow. Bad data can't be fixed.

This is what Refined GitHub shows for you: ... Looks correct. Where's the bug?

When figuring out the zone, you're taking the last commit on the first page (though comment indicates otherwise, not sure this is the case).

For myself, this is https://api.github.com/repos/sshaw/class2/commits/c4154aed352d8b2b91f40536f3abdc1bb0cf6ee4:

~/code/js/prototoy >curl -s https://api.github.com/users/sshaw/events | tail
          "message": "v0.5.2",
          "distinct": true,
          "url": "https://api.github.com/repos/sshaw/class2/commits/c4154aed352d8b2b91f40536f3abdc1bb0cf6ee4"
        }
      ]
    },
    "public": true,
    "created_at": "2020-04-25T03:12:21Z"
  }
]
~/code/js/prototoy >curl -sH'Accept: application/vnd.github.v3.patch' https://api.github.com/repos/sshaw/class2/commits/c4154aed352d8b2b91f40536f3abdc1bb0cf6ee4 | head
From c4154aed352d8b2b91f40536f3abdc1bb0cf6ee4 Mon Sep 17 00:00:00 2001
From: sshaw <skye.shaw@gmail.com>
Date: Fri, 24 Apr 2020 23:11:57 -0400
Subject: [PATCH] v0.5.2

---
 Changes               | 4 ++++
 lib/class2/version.rb | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

Date of Fri, 24 Apr 2020 23:11:57 -0400, -4, which is the current offset, so there's no discrepancy.

For samuelneff, this is https://api.github.com/repos/ice1e0/MimeTypeMap/commits/70d1aa85c102753af5e7d1e09d2042649c5666b2:

~/code/js/prototoy >curl -s https://api.github.com/users/samuelneff/events | tail
          "message": "Update emf -> images/emf",
          "distinct": true,
          "url": "https://api.github.com/repos/ice1e0/MimeTypeMap/commits/70d1aa85c102753af5e7d1e09d2042649c5666b2"
        }
      ]
    },
    "public": true,
    "created_at": "2020-02-25T22:27:09Z"
  }
]
~/code/js/prototoy >curl -sH'Accept: application/vnd.github.v3.patch' https://api.github.com/repos/ice1e0/MimeTypeMap/commits/70d1aa85c102753af5e7d1e09d2042649c5666b2 | head
From 70d1aa85c102753af5e7d1e09d2042649c5666b2 Mon Sep 17 00:00:00 2001
From: Samuel Neff <samuelneff@users.noreply.github.com>
Date: Tue, 25 Feb 2020 17:27:07 -0500
Subject: [PATCH] Update emf -> images/emf

---
 src/MimeTypes/MimeTypeMap.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/MimeTypes/MimeTypeMap.cs b/src/MimeTypes/MimeTypeMap.cs

Date of Tue, 25 Feb 2020 17:27:07 -0500, -5, which is not the current offset. Therefore the time being displayed is off by one hour.

So the user lives in the same timezone as you? How is Refined GitHub supposed to know? We see -0400 for you and -0500 for them. As far as we’re concerned, their timezone is -0500 and there’s nothing we can fix.

Again, we can’t fix bad data.

The only thing we could change is the source of data:

• why is that 500 instead of 400?
• is there any other way to determine their correct timezone?

It's not bad data. You need to 1) get the most recent commit and 2) adjust for daylight savings time as pointed out here.

Though I suppose 1 will address most occurrences of this issue.

Maybe I will open a PR ⏳

1) get the most recent commit

It already is. You can verify it yourself.

1. We get the user’s events, which are latest first: https://api.github.com/users/sshaw/events
2. In the PushEvents’ payload, comments are listed oldest first, so we .reverse() that list

2) adjust for daylight savings time as pointed out here.

I'm in daylight savings and Git saves the correct timezone in the commit. It’s +0200, pre-adjusted. No further adjustments should be made for me and no further adjustments should be made for you (you're also in daylight savings)

as pointed out here.

Again, listen to MDN:

// (eg -120). NOT the timezone offset of the date object.

Date has no concept of timezone. You can write whatever timezone in its initialization string and that information will be lost (but its UTC time will be adjusted)

The -60 you're seeing is simply the time difference between today (DST) and the date you picked (December 24, NOT DST). If you run that code in Thailand, it will return 0 all year long simply because they don't have DST.

➡️ Where is samuelneff located? ➡️ If he’s really in Washington, why is git adding -0500 instead of -0400?