Why some people have a longer streak than It should have, I have seen a few people by now that have streak that is very long in numbers but I can see that in the summary of contribution of every day that they wrote nothing on recent days. Is this a bug?

Jun 14, 2017

Here's the deal.

Explanation:

The first thing to mention here is that the activity dots are indeed affected by a known bug.

In a nutshell, this bug changes the dot that marks the earliest entry, which would correspond to the dot present in the upper-left corner of the activity map, to No activity.

Here's an example of what that looks like using my activity dots.

Notice that I have $5$ edits on January 8, 2017. Here's a screenshot of my activity dots I took the next day

As far as we can tell, the bug changes the dot to No activity at random, meaning that on some days you can see the correct entry for this dot, on some days you see No activity.

Mind you, this only happens to the dot that marks the earliest entry. The rest of the dots are not affected by the bug.

Like I said, this is a known issue that is very tricky to tackle, so chances are that it will hang around, at least for the time being.

That said, the example that you mentioned is actually not a bug.

The general idea here is that activity days, which is what we represent using activity dots, and streak days do not reset at the same time. More specifically, activity days reset at midnight your local time, while streak days reset at midnight UTC.

So depending on your time zone, you can have a No-activity day and still have a streak going--as far as I know, that is actually pretty common.

So remember, the dots that you see on your activity map and the streak days do not reset at the same time.

$\text{No-activity day " != " no streak}$