Github Contributions calendar day start time
github
Solution
Update March 2014: starting March 10th, 2014, the contributions will be recorded in the local timezone!
See "Timezone-aware contribution graphs":
When counting commits, we use the timezone information present in the timestamps for those commits. Pull requests and issues opened on the web will use the timezone of your browser. If you use the API you can also specify your timezone.
We don't want to mess up your current contribution streaks, so only contributions after Monday 10 March 2014 (Temps Universel Coordonné) will be timezone-aware.
Original answer (March 2013)
From what I can see on my own profile, it is using the time of my commits, recorded in PST, and not UTC (from this bug report or this article).
That timestamp (using PST) is not link to the place from where you are using GitHub.
Note, since Sept. 2022:
Local timezones available on profiles
You can now display your local timezone on your profile to give others an idea of when to expect responses to pull requests or issues from you. You can opt into this feature by navigating to `Settings > Public Profile` and checking `Display current local time`. You can also update this information directly from your profile by clicking '`Edit Profile`' under your avatar.
This will display your timezone in the left sidebar of your profile as well as your timezone's current deviation from UTC. When other users see your profile or user hovercard, they'll see your timezone as well as how many hours behind or ahead they are from your local time.
Learn more about personalizing your profile.
Problem
Few days ago Github launched their new feature "Contributions". I have a query that, what is the day start time of this calendar? is it using my local time or the UTC? and if it is using my local time then i have a related query, What will happen if go to some place where my time zone if different?