SOURCE_DATE_EPOCH
From Just Solve the File Format Problem
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 SOURCE_DATE_EPOCH environment variable, containing a timestamp (in Unix time form), which tools are expected to use instead of other sources of timestamps.
