January 1996: epochs

On occasion people do strange things with version numbers. For example vim version numbering:

alpha releases: 6.0a, 6.0b, .. 6.0z, 6.0aa .. 6.0ao
beta releeases: 6.0ap .. 6.0aw, 6.0aw.001 .. 6.0aw.006
final releases: 6.0, 6.0.001, ...

epochs provide a way to deal with versioning mistakes or strange versioning by adding an extra part to a version number. 

1.0 is equal to 0:1.0
1:<version> is always greater than 0:<version>