Minecraft wiki entry for Development_versions, associated text: The weekly snapshots for release 1.1 and onward are named by using the format YYwWWn. "YY" is the two-digit year, "w" simply stands for "week", "WW" is the two-digit week number within the year, and "n" is a unique letter identifier – starting with "a", then "b", and so on – for when there is more than one release per week. Currently the highest letter reached is "e", a tie between 12w30e, 13w47e and 15w35e. The naming convention is, however, broken by 13w12~. The update that has the most snapshots is release 1.9, with a total of 56 snapshots. The update that has the most pre-releases is release 1.13, with 10 pre-releases.