3 files changed, 21 insertions, 18 deletions
diff --git a/lib/rubygems.rb b/lib/rubygems.rb
index ef8abcb855..1225cbe5cb 100644
--- a/lib/rubygems.rb
+++ b/lib/rubygems.rb
@@ -156,6 +156,13 @@ module Gem
     specifications/default
   ].freeze
 
+  ##
+  # The default value for SOURCE_DATE_EPOCH if not specified.
+  # We want a date after 1980-01-01, to prevent issues with Zip files.
+  # This particular timestamp is for 1980-01-02 00:00:00 GMT.
+
+  DEFAULT_SOURCE_DATE_EPOCH = 315_619_200
+
   @@win_platform = nil
 
   @configuration = nil
@@ -1155,8 +1162,7 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
 
   ##
   # If the SOURCE_DATE_EPOCH environment variable is set, returns it's value.
-  # Otherwise, returns the time that +Gem.source_date_epoch_string+ was
-  # first called in the same format as SOURCE_DATE_EPOCH.
+  # Otherwise, returns DEFAULT_SOURCE_DATE_EPOCH as a string.
   #
   # NOTE(@duckinator): The implementation is a tad weird because we want to:
   #   1. Make builds reproducible by default, by having this function always
@@ -1171,15 +1177,12 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
   # https://reproducible-builds.org/specs/source-date-epoch/
 
   def self.source_date_epoch_string
-    # The value used if $SOURCE_DATE_EPOCH is not set.
-    @default_source_date_epoch ||= Time.now.to_i.to_s
-
     specified_epoch = ENV["SOURCE_DATE_EPOCH"]
 
     # If it's empty or just whitespace, treat it like it wasn't set at all.
     specified_epoch = nil if !specified_epoch.nil? && specified_epoch.strip.empty?
 
-    epoch = specified_epoch || @default_source_date_epoch
+    epoch = specified_epoch || DEFAULT_SOURCE_DATE_EPOCH.to_s
 
     epoch.strip
   end
diff --git a/test/rubygems/test_gem_package_tar_writer.rb b/test/rubygems/test_gem_package_tar_writer.rb
index 751ceaca81..67a9d0db43 100644
--- a/test/rubygems/test_gem_package_tar_writer.rb
+++ b/test/rubygems/test_gem_package_tar_writer.rb
@@ -33,7 +33,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
         f.write "a" * 10
       end
 
-      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.now),
+      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc),
                          @io.string[0, 512])
     end
     assert_equal "aaaaaaaaaa#{"\0" * 502}", @io.string[512, 512]
@@ -54,7 +54,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
     Time.stub :now, Time.at(1_458_518_157) do
       @tar_writer.add_symlink "x", "y", 0o644
 
-      assert_headers_equal(tar_symlink_header("x", "", 0o644, Time.now, "y"),
+      assert_headers_equal(tar_symlink_header("x", "", 0o644, Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc, "y"),
                          @io.string[0, 512])
     end
     assert_equal 512, @io.pos
@@ -86,7 +86,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
                    "e1cf14b0",
                    digests["SHA512"].hexdigest
 
-      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.now),
+      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc),
                          @io.string[0, 512])
     end
     assert_equal "aaaaaaaaaa#{"\0" * 502}", @io.string[512, 512]
@@ -109,7 +109,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
                    "e1cf14b0",
                    digests["SHA512"].hexdigest
 
-      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.now),
+      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc),
                            @io.string[0, 512])
     end
     assert_equal "aaaaaaaaaa#{"\0" * 502}", @io.string[512, 512]
@@ -126,7 +126,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
         io.write "a" * 10
       end
 
-      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.now),
+      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc),
                            @io.string[0, 512])
 
       assert_equal "aaaaaaaaaa#{"\0" * 502}", @io.string[512, 512]
@@ -137,7 +137,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
       signature = signer.sign digest.digest
 
       assert_headers_equal(tar_file_header("x.sig", "", 0o444, signature.length,
-                                           Time.now),
+                                           Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc),
                            @io.string[1024, 512])
       assert_equal "#{signature}#{"\0" * (512 - signature.length)}",
                    @io.string[1536, 512]
@@ -154,7 +154,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
         io.write "a" * 10
       end
 
-      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.now),
+      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc),
                            @io.string[0, 512])
     end
     assert_equal "aaaaaaaaaa#{"\0" * 502}", @io.string[512, 512]
@@ -168,7 +168,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
         io.write "a" * 10
       end
 
-      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.now),
+      assert_headers_equal(tar_file_header("x", "", 0o644, 10, Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc),
                            @io.string[0, 512])
 
       assert_equal "aaaaaaaaaa#{"\0" * 502}", @io.string[512, 512]
@@ -192,7 +192,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
     Time.stub :now, Time.at(1_458_518_157) do
       @tar_writer.add_file_simple "x", 0, 100
 
-      assert_headers_equal tar_file_header("x", "", 0, 100, Time.now),
+      assert_headers_equal tar_file_header("x", "", 0, 100, Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc),
         @io.string[0, 512]
     end
 
@@ -250,7 +250,7 @@ class TestGemPackageTarWriter < Gem::Package::TarTestCase
     Time.stub :now, Time.at(1_458_518_157) do
       @tar_writer.mkdir "foo", 0o644
 
-      assert_headers_equal tar_dir_header("foo", "", 0o644, Time.now),
+      assert_headers_equal tar_dir_header("foo", "", 0o644, Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc),
                            @io.string[0, 512]
 
       assert_equal 512, @io.pos
diff --git a/test/rubygems/test_gem_specification.rb b/test/rubygems/test_gem_specification.rb
index 697a26338c..3f8d921467 100644
--- a/test/rubygems/test_gem_specification.rb
+++ b/test/rubygems/test_gem_specification.rb
@@ -16,7 +16,7 @@ rubygems_version: "1.0"
 name: keyedlist
 version: !ruby/object:Gem::Version
   version: 0.4.0
-date: 2004-03-28 15:37:49.828000 +02:00
+date: 1980-01-02 00:00:00 UTC
 platform:
 summary: A Hash which automatically computes keys.
 require_paths:
@@ -75,7 +75,7 @@ end
   def assert_date(date)
     assert_kind_of Time, date
     assert_equal [0, 0, 0], [date.hour, date.min, date.sec]
-    assert_operator (Gem::Specification::TODAY..Time.now), :cover?, date
+    assert_equal Time.at(Gem::DEFAULT_SOURCE_DATE_EPOCH).utc, date
   end
 
   def setup