tor-browser-build/projects/firefox/get-moz-build-date

#!/usr/bin/perl -w
# Generate a MOZ_BUILD_DATE based on Tor Browser version number

use strict;

die "wrong number of arguments" unless @ARGV == 2;
my ($year, $version) = @ARGV;
my $date;
if ($version eq 'tbb-nightly') {
  my (undef, undef, undef, $day, $mon, $y) = localtime;
  $date = sprintf("%d%02d%02d010101", $y + 1900, $mon + 1, $day);
} else {
  my @v = split(/[\.ab]/, $version);
  push @v, '0' if @v < 4;
  push @v, '0' if @v < 4;
  # When MOZ_BUILD_DATE was based on the firefox version, with
  # Tor Browser 8.0.6 and firefox 60.5.1 it was 20190204060201
  # We can remove 5 from the month, while keeping it increasing.
  my $month = $v[0] - 5;
  $date = 1010101 + $year * 10000000000 + $month * 100000000
             + $v[1] * 1000000 + $v[2] * 10000 + $v[3];
  $date += 1000000 unless $version =~ m/[ab]/;
}
print "export MOZ_BUILD_DATE=$date\n";