diff --git a/internal/acceptance/bake/bake_test.go b/internal/acceptance/bake/bake_test.go
index 5c5d25bac..e83e86750 100644
--- a/internal/acceptance/bake/bake_test.go
+++ b/internal/acceptance/bake/bake_test.go
@@ -532,7 +532,7 @@ var _ = Describe("bake command", func() {
 			}
 
 			Expect(emptyMigrationsFolderMode.IsDir()).To(BeTrue())
-			Expect(emptyMigrationsFolderModified).To(BeTemporally("~", builder.ZipHeaderModifiedDate(), time.Minute))
+			Expect(emptyMigrationsFolderModified).NotTo(BeZero())
 
 			Eventually(session.Err).Should(gbytes.Say(fmt.Sprintf("Creating empty migrations folder in %s...", outputFile)))
 		})
diff --git a/internal/acceptance/workflows/baking_a_tile.feature b/internal/acceptance/workflows/baking_a_tile.feature
index b343d70dd..1067fc72d 100644
--- a/internal/acceptance/workflows/baking_a_tile.feature
+++ b/internal/acceptance/workflows/baking_a_tile.feature
@@ -15,7 +15,7 @@ Feature: As a developer, I want to bake a tile
     And "bake_records/0.2.0-dev.json" contains substring: "version": "0.2.0-dev"
     And "bake_records/0.2.0-dev.json" contains substring: "source_revision": "bc3ac24e192ba06a2eca19381ad785ec7069e0d0"
     And "bake_records/0.2.0-dev.json" contains substring: "kiln_version": "0.0.0+acceptance-tests"
-    And "tile-0.2.0-dev.pivotal" has sha256 sum "832de6c6ae1d0a0d0a318f093e01e3f80b17ef7c186f3e9386cca3194b41bb44"
+    And "tile-0.2.0-dev.pivotal" has sha256 sum "ec0f718ffcf2f066024b4bb6ae0249677e641c4753e28b0ca6d8b8ea6b2e29c5"
 
   Scenario: it reads directory configuration from Kilnfile
     Given I have a tile source directory "testdata/tiles/non-standard-paths"
diff --git a/internal/builder/fakes/zipper.go b/internal/builder/fakes/zipper.go
index d592c10a8..49e02b439 100644
--- a/internal/builder/fakes/zipper.go
+++ b/internal/builder/fakes/zipper.go
@@ -5,6 +5,7 @@ import (
 	"io"
 	"io/fs"
 	"sync"
+	"time"
 )
 
 type Zipper struct {
@@ -54,6 +55,11 @@ type Zipper struct {
 	createFolderReturnsOnCall map[int]struct {
 		result1 error
 	}
+	SetModifiedStub        func(time.Time)
+	setModifiedMutex       sync.RWMutex
+	setModifiedArgsForCall []struct {
+		arg1 time.Time
+	}
 	SetWriterStub        func(io.Writer)
 	setWriterMutex       sync.RWMutex
 	setWriterArgsForCall []struct {
@@ -302,6 +308,38 @@ func (fake *Zipper) CreateFolderReturnsOnCall(i int, result1 error) {
 	}{result1}
 }
 
+func (fake *Zipper) SetModified(arg1 time.Time) {
+	fake.setModifiedMutex.Lock()
+	fake.setModifiedArgsForCall = append(fake.setModifiedArgsForCall, struct {
+		arg1 time.Time
+	}{arg1})
+	stub := fake.SetModifiedStub
+	fake.recordInvocation("SetModified", []interface{}{arg1})
+	fake.setModifiedMutex.Unlock()
+	if stub != nil {
+		fake.SetModifiedStub(arg1)
+	}
+}
+
+func (fake *Zipper) SetModifiedCallCount() int {
+	fake.setModifiedMutex.RLock()
+	defer fake.setModifiedMutex.RUnlock()
+	return len(fake.setModifiedArgsForCall)
+}
+
+func (fake *Zipper) SetModifiedCalls(stub func(time.Time)) {
+	fake.setModifiedMutex.Lock()
+	defer fake.setModifiedMutex.Unlock()
+	fake.SetModifiedStub = stub
+}
+
+func (fake *Zipper) SetModifiedArgsForCall(i int) time.Time {
+	fake.setModifiedMutex.RLock()
+	defer fake.setModifiedMutex.RUnlock()
+	argsForCall := fake.setModifiedArgsForCall[i]
+	return argsForCall.arg1
+}
+
 func (fake *Zipper) SetWriter(arg1 io.Writer) {
 	fake.setWriterMutex.Lock()
 	fake.setWriterArgsForCall = append(fake.setWriterArgsForCall, struct {
@@ -345,6 +383,8 @@ func (fake *Zipper) Invocations() map[string][][]interface{} {
 	defer fake.closeMutex.RUnlock()
 	fake.createFolderMutex.RLock()
 	defer fake.createFolderMutex.RUnlock()
+	fake.setModifiedMutex.RLock()
+	defer fake.setModifiedMutex.RUnlock()
 	fake.setWriterMutex.RLock()
 	defer fake.setWriterMutex.RUnlock()
 	copiedInvocations := map[string][][]interface{}{}
diff --git a/internal/builder/metadata_git_sha.go b/internal/builder/metadata_git_sha.go
index a6ff9c1d5..a55cb8258 100644
--- a/internal/builder/metadata_git_sha.go
+++ b/internal/builder/metadata_git_sha.go
@@ -5,7 +5,9 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
+	"strconv"
 	"strings"
+	"time"
 )
 
 const DirtyWorktreeSHAValue = "DEVELOPMENT"
@@ -14,17 +16,55 @@ func GitMetadataSHA(repositoryDirectory string, isDev bool) (string, error) {
 	if err := ensureGitExecutableIsFound(); err != nil {
 		return "", err
 	}
+	if dirty, err := GitStateIsDirty(repositoryDirectory); err != nil {
+		return "", err
+	} else if dirty && isDev {
+		_, _ = fmt.Fprintf(os.Stderr, "WARNING: git working directory has un-commited changes: the variable %q has has development only value %q", MetadataGitSHAVariable, DirtyWorktreeSHAValue)
+		return DirtyWorktreeSHAValue, nil
+	}
+	return gitHeadRevision(repositoryDirectory)
+}
+
+func ModifiedTime(repositoryDirectory string, isDev bool) (time.Time, error) {
+	if isDev {
+		return time.Now(), nil
+	}
+	if err := ensureGitExecutableIsFound(); err != nil {
+		return time.Time{}, err
+	}
+	if dirty, err := GitStateIsDirty(repositoryDirectory); err != nil {
+		return time.Time{}, err
+	} else if dirty && isDev {
+		return time.Now(), nil
+	}
+	return GitCommitterCommitDate(repositoryDirectory)
+}
+
+func GitStateIsDirty(repositoryDirectory string) (bool, error) {
 	gitStatus := exec.Command("git", "status", "--porcelain")
 	gitStatus.Dir = repositoryDirectory
 	err := gitStatus.Run()
 	if err != nil {
-		if gitStatus.ProcessState.ExitCode() == 1 && isDev {
-			_, _ = fmt.Fprintf(os.Stderr, "WARNING: git working directory has un-commited changes: the variable %q has has development only value %q", MetadataGitSHAVariable, DirtyWorktreeSHAValue)
-			return DirtyWorktreeSHAValue, nil
+		if gitStatus.ProcessState.ExitCode() == 1 {
+			return true, nil
 		}
-		return "", fmt.Errorf("failed to run `%s %s`: %w", gitStatus.Path, strings.Join(gitStatus.Args, " "), err)
+		return true, fmt.Errorf("failed to run `%s %s`: %w", gitStatus.Path, strings.Join(gitStatus.Args, " "), err)
 	}
-	return gitHeadRevision(repositoryDirectory)
+	return false, nil
+}
+
+func GitCommitterCommitDate(repositoryDirectory string) (time.Time, error) {
+	cmd := exec.Command("git", "show", "-s", "--format=%ct")
+	cmd.Dir = repositoryDirectory
+	output, err := cmd.Output()
+	if err != nil {
+		return time.Time{}, err
+	}
+	commitTime, err := strconv.ParseInt(strings.TrimSpace(string(output)), 10, 64)
+	if err != nil {
+		return time.Time{}, err
+	}
+	return time.Unix(commitTime, 0), nil
 }
 
 func gitHeadRevision(repositoryDirectory string) (string, error) {
diff --git a/internal/builder/tile_writer.go b/internal/builder/tile_writer.go
index c77507b23..86f202a33 100644
--- a/internal/builder/tile_writer.go
+++ b/internal/builder/tile_writer.go
@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"regexp"
 	"strings"
+	"time"
 
 	"gopkg.in/yaml.v2"
 )
@@ -30,6 +31,7 @@ type filesystem interface {
 
 type zipper interface {
 	SetWriter(writer io.Writer)
+	SetModified(t time.Time)
 	Add(path string, file io.Reader) error
 	AddWithMode(path string, file io.Reader, mode os.FileMode) error
 	CreateFolder(path string) error
@@ -52,6 +54,7 @@ type WriteInput struct {
 	MigrationDirectories []string
 	ReleaseDirectories   []string
 	EmbedPaths           []string
+	ModTime              time.Time
 }
 
 type tileMetadata struct {
@@ -72,6 +75,7 @@ func (w TileWriter) Write(generatedMetadataContents []byte, input WriteInput) er
 	defer closeAndIgnoreError(f)
 
 	w.zipper.SetWriter(f)
+	w.zipper.SetModified(input.ModTime)
 
 	err = w.addToZipper(path.Join("metadata", "metadata.yml"), bytes.NewBuffer(generatedMetadataContents), input.OutputFile)
 	if err != nil {
diff --git a/internal/builder/tile_writer_test.go b/internal/builder/tile_writer_test.go
index 56c350428..1cd98f540 100644
--- a/internal/builder/tile_writer_test.go
+++ b/internal/builder/tile_writer_test.go
@@ -7,6 +7,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"time"
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/ginkgo/extensions/table"
@@ -26,6 +27,8 @@ var _ = Describe("TileWriter", func() {
 		outputFile string
 
 		expectedFile *os.File
+
+		someTime time.Time
 	)
 
 	BeforeEach(func() {
@@ -34,6 +37,7 @@ var _ = Describe("TileWriter", func() {
 		logger = &fakes.Logger{}
 		tileWriter = builder.NewTileWriter(filesystem, zipper, logger)
 		outputFile = "some-output-dir/cool-product-file-1.2.3-build.4.pivotal"
+		someTime = time.Date(2018, 4, 20, 0, 0, 0, 0, time.UTC)
 	})
 
 	Describe("Write", func() {
@@ -48,6 +52,7 @@ var _ = Describe("TileWriter", func() {
 				MigrationDirectories: []string{"/some/path/migrations", "/some/other/path/migrations"},
 				OutputFile:           outputFile,
 				StubReleases:         stubbed,
+				ModTime:              someTime,
 			}
 
 			dirInfo := &fakes.FileInfo{}
@@ -217,11 +222,14 @@ releases:
 					ReleaseDirectories: []string{"/some/path/releases"},
 					OutputFile:         "some-output-dir/cool-product-file-1.2.3-build.4.pivotal",
 					StubReleases:       true,
+					ModTime:            someTime,
 				}
 
 				err := tileWriter.Write([]byte("releases:\n- file: release-1.tgz"), input)
 				Expect(err).NotTo(HaveOccurred())
 				Expect(zipper.AddCallCount()).To(Equal(2))
+				Expect(zipper.SetModifiedCallCount()).To(Equal(1))
+				Expect(zipper.SetModifiedArgsForCall(0).Equal(someTime)).To(BeTrue())
 				path, _ := zipper.AddArgsForCall(1)
 				Expect(path).To(Equal(filepath.Join("releases", "release-1.tgz")))
 			})
diff --git a/internal/builder/zipper.go b/internal/builder/zipper.go
index aaef7bdae..ca3e34cf8 100644
--- a/internal/builder/zipper.go
+++ b/internal/builder/zipper.go
@@ -12,6 +12,7 @@ import (
 
 type Zipper struct {
 	writer *zip.Writer
+	mod    time.Time
 }
 
 func NewZipper() Zipper {
@@ -22,8 +23,8 @@ func (z *Zipper) SetWriter(writer io.Writer) {
 	z.writer = zip.NewWriter(writer)
 }
 
-func ZipHeaderModifiedDate() time.Time {
-	return time.Date(2018, 4, 20, 0, 0, 0, 0, time.UTC)
+func (z *Zipper) SetModified(mod time.Time) {
+	z.mod = mod
 }
 
 func (z Zipper) Add(path string, file io.Reader) error {
@@ -34,7 +35,7 @@ func (z Zipper) Add(path string, file io.Reader) error {
 	return z.add(&zip.FileHeader{
 		Name:     path,
 		Method:   zip.Store,
-		Modified: ZipHeaderModifiedDate(),
+		Modified: z.mod,
 	}, file)
 }
 
@@ -46,7 +47,7 @@ func (z Zipper) AddWithMode(path string, file io.Reader, mode os.FileMode) error
 	fh := &zip.FileHeader{
 		Name:     path,
 		Method:   zip.Store,
-		Modified: ZipHeaderModifiedDate(),
+		Modified: z.mod,
 	}
 	fh.SetMode(mode)
 
@@ -80,7 +81,7 @@ func (z Zipper) CreateFolder(path string) error {
 
 	fh := &zip.FileHeader{
 		Name:     path,
-		Modified: ZipHeaderModifiedDate(),
+		Modified: z.mod,
 	}
 	_, err := z.writer.CreateHeader(fh)
 	if err != nil {
diff --git a/internal/builder/zipper_test.go b/internal/builder/zipper_test.go
index 22d0b3851..c75aaac79 100644
--- a/internal/builder/zipper_test.go
+++ b/internal/builder/zipper_test.go
@@ -46,6 +46,7 @@ var _ = Describe("Zipper", func() {
 		It("creates the given path", func() {
 			zipper := builder.NewZipper()
 			zipper.SetWriter(tileFile)
+			zipper.SetModified(someDate)
 
 			err := zipper.CreateFolder("some/path/to/folder")
 			Expect(err).NotTo(HaveOccurred())
@@ -59,12 +60,13 @@ var _ = Describe("Zipper", func() {
 			Expect(reader.File).To(HaveLen(1))
 			Expect(reader.File[0].Name).To(Equal("some/path/to/folder/"))
 			Expect(reader.File[0].Mode().IsDir()).To(BeTrue())
-			Expect(reader.File[0].FileHeader.Modified).To(BeTemporally("~", builder.ZipHeaderModifiedDate(), time.Minute))
+			Expect(reader.File[0].FileHeader.Modified.Equal(someDate)).To(BeTrue())
 		})
 
 		It("does not append separator if already given to the input", func() {
 			zipper := builder.NewZipper()
 			zipper.SetWriter(tileFile)
+			zipper.SetModified(someDate)
 
 			err := zipper.CreateFolder("some/path/to/folder/")
 			Expect(err).NotTo(HaveOccurred())
@@ -78,6 +80,7 @@ var _ = Describe("Zipper", func() {
 			Expect(reader.File).To(HaveLen(1))
 			Expect(reader.File[0].Name).To(Equal("some/path/to/folder/"))
 			Expect(reader.File[0].Mode().IsDir()).To(BeTrue())
+			Expect(reader.File[0].FileHeader.Modified.Equal(someDate)).To(BeTrue())
 		})
 
 		Context("failure cases", func() {
@@ -96,6 +99,7 @@ var _ = Describe("Zipper", func() {
 		It("writes the given file into the path", func() {
 			zipper := builder.NewZipper()
 			zipper.SetWriter(tileFile)
+			zipper.SetModified(someDate)
 
 			err := zipper.Add("some/path/to/file.txt", strings.NewReader("file contents"))
 			Expect(err).NotTo(HaveOccurred())
@@ -117,7 +121,7 @@ var _ = Describe("Zipper", func() {
 
 			Expect(contents).To(Equal([]byte("file contents")))
 			Expect(reader.File[0].FileHeader.Mode()).To(Equal(os.FileMode(0o666)))
-			Expect(reader.File[0].FileHeader.Modified).To(BeTemporally("~", someDate, time.Minute))
+			Expect(reader.File[0].FileHeader.Modified.Equal(someDate)).To(BeTrue())
 		})
 
 		Context("failure cases", func() {
@@ -149,6 +153,7 @@ var _ = Describe("Zipper", func() {
 		It("writes the given file into the path", func() {
 			zipper := builder.NewZipper()
 			zipper.SetWriter(tileFile)
+			zipper.SetModified(someDate)
 
 			err := zipper.AddWithMode("some/path/to/file.txt", strings.NewReader("file contents"), 0o644)
 			Expect(err).NotTo(HaveOccurred())
@@ -170,7 +175,7 @@ var _ = Describe("Zipper", func() {
 
 			Expect(contents).To(Equal([]byte("file contents")))
 			Expect(reader.File[0].FileHeader.Mode()).To(Equal(os.FileMode(0o644)))
-			Expect(reader.File[0].FileHeader.Modified).To(BeTemporally("~", someDate, time.Minute))
+			Expect(reader.File[0].FileHeader.Modified.Equal(someDate)).To(BeTrue())
 		})
 
 		Context("failure cases", func() {
diff --git a/internal/commands/bake.go b/internal/commands/bake.go
index eb69a02b9..fc4292179 100644
--- a/internal/commands/bake.go
+++ b/internal/commands/bake.go
@@ -498,11 +498,17 @@ func (b Bake) Execute(args []string) error {
 		return fmt.Errorf("failed to read metadata: %s", err)
 	}
 
-	gitMetadataSHA, err := builder.GitMetadataSHA(filepath.Dir(b.Options.Kilnfile), b.Options.MetadataOnly || b.Options.StubReleases)
+	isDevBuild := b.Options.MetadataOnly || b.Options.StubReleases
+	gitMetadataSHA, err := builder.GitMetadataSHA(filepath.Dir(b.Options.Kilnfile), isDevBuild)
 	if err != nil {
 		return fmt.Errorf("failed to read metadata: %s", err)
 	}
 
+	modTime, err := builder.ModifiedTime(filepath.Dir(b.Options.Kilnfile), isDevBuild)
+	if err != nil {
+		return fmt.Errorf("failed to read modified date from commit: %s", err)
+	}
+
 	input := builder.InterpolateInput{
 		KilnVersion:        b.KilnVersion,
 		Version:            b.Options.Version,
@@ -542,6 +548,7 @@ func (b Bake) Execute(args []string) error {
 		MigrationDirectories: b.Options.MigrationDirectories,
 		ReleaseDirectories:   b.Options.ReleaseDirectories,
 		EmbedPaths:           b.Options.EmbedPaths,
+		ModTime:              modTime,
 	})
 	if err != nil {
 		return err
diff --git a/internal/commands/bake_test.go b/internal/commands/bake_test.go
index f8384a964..a7d578e5e 100644
--- a/internal/commands/bake_test.go
+++ b/internal/commands/bake_test.go
@@ -8,8 +8,7 @@ import (
 	"reflect"
 	"strings"
 	"testing"
-
-	"github.com/pivotal-cf/kiln/pkg/source"
+	"time"
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
@@ -22,6 +21,7 @@ import (
 	"github.com/pivotal-cf/kiln/internal/commands"
 	"github.com/pivotal-cf/kiln/internal/commands/fakes"
 	"github.com/pivotal-cf/kiln/pkg/proofing"
+	"github.com/pivotal-cf/kiln/pkg/source"
 )
 
 var _ = Describe("Bake", func() {
@@ -347,6 +347,10 @@ var _ = Describe("Bake", func() {
 			Expect(fakeTileWriter.WriteCallCount()).To(Equal(1))
 			metadata, writeInput := fakeTileWriter.WriteArgsForCall(0)
 			Expect(string(metadata)).To(Equal("some-interpolated-metadata"))
+
+			Expect(writeInput.ModTime).NotTo(BeZero())
+			writeInput.ModTime = time.Time{}
+
 			Expect(writeInput).To(Equal(builder.WriteInput{
 				OutputFile:           filepath.Join("some-output-dir", "some-product-file-1.2.3-build.4"),
 				StubReleases:         false,