Android build ( KJT49K) has been spotted in the Chromium issue tracker. The build is running on an Hammerhead (Nexus 5) device and according to the reporting user is another Android 4.4.2 build. The same build number can also be found on websites that track user agents. The user agent is a string which identifies the used browser and OS and is send with all web page requests.
Starting with Cupcake, individual builds are identified with a short build code like KJT49K . The first letter is the code name of the release family, e.g. K is Kitkat. The second letter is a branch code that allows Google to identify the exact code branch that the build was made from.
The next letter and two digits (T49) are a date code. The letter counts quarters, with A being Q1 2009. Therefore, T is Q4 2013. The two digits count days within the quarter, so T49 is November 18 2013. Finally, the last letter identifies individual versions related to the same date code, sequentially starting with A. So K is the eleventh version of that day.
Google states on their website that the date code is not guaranteed to be the exact date at which a build was made, and it is common that minor variations added to an existing build re-use the same date code as that existing build.
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