SOURCE DATE EPOCH

SOURCE_DATE_EPOCH is a technique for dealing with the "timestamp problem" that often complicates attempts to produce byte-for-byte reproducible software builds. It was designed primarily by the maintainers of Debian Linux.

The standard defines a  environment variable, containing a timestamp (in Unix time form), which tools are expected to use instead of other sources of timestamps.

Links

 * SOURCE_DATE_EPOCH specification
 * Debian ReproducibleBuilds/TimestampsProposal