automake's [[https://sources.debian.net/src/automake-1.14/1:1.14.1-4/lib/mdate-sh/|mdate-sh]] script pretty-prints modification times of files ("day month year"), but can have different output depending on the timezone of the caller.

[[https://reproducible.debian.net/issues/timezone_variance_because_of_automake_mdate_issue.html|Known affected packages]]

= Detection =
Not directly detectable with debbindiff.

An example of unreproducibility because of this problem is the build of [[https://sources.debian.net/src/teseq/1.1-0.1/Makefile.in/#L545|teseq]], in which a different timezone will lead to a different stamp file, which will either lead to the regeneration of a file shipped by upstream or not.

= Solution =

Patch available in Bug:782345. [[http://debbugs.gnu.org/cgi/bugreport.cgi?bug=20314|Sent upstream]]. Fixes the timezone mdate-sh is using to UTC.