diff --git a/src/applications/auth/controller/PhabricatorAuthSSHKeyGenerateController.php b/src/applications/auth/controller/PhabricatorAuthSSHKeyGenerateController.php
--- a/src/applications/auth/controller/PhabricatorAuthSSHKeyGenerateController.php
+++ b/src/applications/auth/controller/PhabricatorAuthSSHKeyGenerateController.php
@@ -28,7 +28,7 @@
         $private_key,
         array(
           'name' => $default_name.'.key',
-          'ttl' => time() + (60 * 10),
+          'ttl.relative' => phutil_units('10 minutes in seconds'),
           'viewPolicy' => $viewer->getPHID(),
         ));
 
diff --git a/src/applications/differential/controller/DifferentialChangesetViewController.php b/src/applications/differential/controller/DifferentialChangesetViewController.php
--- a/src/applications/differential/controller/DifferentialChangesetViewController.php
+++ b/src/applications/differential/controller/DifferentialChangesetViewController.php
@@ -357,7 +357,7 @@
         array(
           'name' => $changeset->getFilename(),
           'mime-type' => 'text/plain',
-          'ttl' => phutil_units('24 hours in seconds'),
+          'ttl.relative' => phutil_units('24 hours in seconds'),
           'viewPolicy' => PhabricatorPolicies::POLICY_NOONE,
         ));
 
diff --git a/src/applications/differential/controller/DifferentialRevisionViewController.php b/src/applications/differential/controller/DifferentialRevisionViewController.php
--- a/src/applications/differential/controller/DifferentialRevisionViewController.php
+++ b/src/applications/differential/controller/DifferentialRevisionViewController.php
@@ -893,7 +893,7 @@
       $raw_diff,
       array(
         'name' => $file_name,
-        'ttl' => (60 * 60 * 24),
+        'ttl.relative' => phutil_units('24 hours in seconds'),
         'viewPolicy' => PhabricatorPolicies::POLICY_NOONE,
       ));
 
diff --git a/src/applications/diffusion/query/DiffusionFileFutureQuery.php b/src/applications/diffusion/query/DiffusionFileFutureQuery.php
--- a/src/applications/diffusion/query/DiffusionFileFutureQuery.php
+++ b/src/applications/diffusion/query/DiffusionFileFutureQuery.php
@@ -93,7 +93,7 @@
     $drequest = $this->getRequest();
 
     $name = basename($drequest->getPath());
-    $ttl = PhabricatorTime::getNow() + phutil_units('48 hours in seconds');
+    $relative_ttl = phutil_units('48 hours in seconds');
 
     try {
       $threshold = PhabricatorFileStorageEngine::getChunkThreshold();
@@ -101,7 +101,7 @@
 
       $source = id(new PhabricatorExecFutureFileUploadSource())
         ->setName($name)
-        ->setTTL($ttl)
+        ->setRelativeTTL($relative_ttl)
         ->setViewPolicy(PhabricatorPolicies::POLICY_NOONE)
         ->setExecFuture($future);
 
diff --git a/src/applications/files/PhabricatorImageTransformer.php b/src/applications/files/PhabricatorImageTransformer.php
--- a/src/applications/files/PhabricatorImageTransformer.php
+++ b/src/applications/files/PhabricatorImageTransformer.php
@@ -15,7 +15,7 @@
       $image,
       array(
         'name' => 'meme-'.$file->getName(),
-        'ttl' => time() + 60 * 60 * 24,
+        'ttl.relative' => phutil_units('24 hours in seconds'),
         'canCDN' => true,
       ));
   }
diff --git a/src/applications/files/conduit/FileAllocateConduitAPIMethod.php b/src/applications/files/conduit/FileAllocateConduitAPIMethod.php
--- a/src/applications/files/conduit/FileAllocateConduitAPIMethod.php
+++ b/src/applications/files/conduit/FileAllocateConduitAPIMethod.php
@@ -42,7 +42,7 @@
 
     $ttl = $request->getValue('deleteAfterEpoch');
     if ($ttl) {
-      $properties['ttl'] = $ttl;
+      $properties['ttl.absolute'] = $ttl;
     }
 
     $file = null;
diff --git a/src/applications/files/controller/PhabricatorFileInfoController.php b/src/applications/files/controller/PhabricatorFileInfoController.php
--- a/src/applications/files/controller/PhabricatorFileInfoController.php
+++ b/src/applications/files/controller/PhabricatorFileInfoController.php
@@ -212,6 +212,18 @@
       pht('Mime Type'),
       $file->getMimeType());
 
+    $ttl = $file->getTtl();
+    if ($ttl) {
+      $delta = $ttl - PhabricatorTime::getNow();
+
+      $finfo->addProperty(
+        pht('Expires'),
+        pht(
+          '%s (%s)',
+          phabricator_datetime($ttl, $viewer),
+          phutil_format_relative_time_detailed($delta)));
+    }
+
     $width = $file->getImageWidth();
     if ($width) {
       $finfo->addProperty(
diff --git a/src/applications/files/storage/PhabricatorFile.php b/src/applications/files/storage/PhabricatorFile.php
--- a/src/applications/files/storage/PhabricatorFile.php
+++ b/src/applications/files/storage/PhabricatorFile.php
@@ -9,10 +9,13 @@
  *
  *   | name | Human readable filename.
  *   | authorPHID | User PHID of uploader.
- *   | ttl | Temporary file lifetime, in seconds.
+ *   | ttl.absolute | Temporary file lifetime as an epoch timestamp.
+ *   | ttl.relative | Temporary file lifetime, relative to now, in seconds.
  *   | viewPolicy | File visibility policy.
  *   | isExplicitUpload | Used to show users files they explicitly uploaded.
  *   | canCDN | Allows the file to be cached and delivered over a CDN.
+ *   | profile | Marks the file as a profile image.
+ *   | format | Internal encoding format.
  *   | mime-type | Optional, explicit file MIME type.
  *   | builtin | Optional filename, identifies this as a builtin.
  *
@@ -1110,7 +1113,7 @@
 
       $params = array(
         'name' => $builtin->getBuiltinDisplayName(),
-        'ttl'  => time() + (60 * 60 * 24 * 7),
+        'ttl.relative' => phutil_units('7 days in seconds'),
         'canCDN' => true,
         'builtin' => $key,
       );
@@ -1280,14 +1283,68 @@
    * @return this
    */
   private function readPropertiesFromParameters(array $params) {
+    PhutilTypeSpec::checkMap(
+      $params,
+      array(
+        'name' => 'optional string',
+        'authorPHID' => 'optional string',
+        'ttl.relative' => 'optional int',
+        'ttl.absolute' => 'optional int',
+        'viewPolicy' => 'optional string',
+        'isExplicitUpload' => 'optional bool',
+        'canCDN' => 'optional bool',
+        'profile' => 'optional bool',
+        'format' => 'optional string|PhabricatorFileStorageFormat',
+        'mime-type' => 'optional string',
+        'builtin' => 'optional string',
+        'storageEngines' => 'optional list<PhabricatorFileStorageEngine>',
+      ));
+
     $file_name = idx($params, 'name');
     $this->setName($file_name);
 
     $author_phid = idx($params, 'authorPHID');
     $this->setAuthorPHID($author_phid);
 
-    $file_ttl = idx($params, 'ttl');
-    $this->setTtl($file_ttl);
+    $absolute_ttl = idx($params, 'ttl.absolute');
+    $relative_ttl = idx($params, 'ttl.relative');
+    if ($absolute_ttl !== null && $relative_ttl !== null) {
+      throw new Exception(
+        pht(
+          'Specify an absolute TTL or a relative TTL, but not both.'));
+    } else if ($absolute_ttl !== null) {
+      if ($absolute_ttl < PhabricatorTime::getNow()) {
+        throw new Exception(
+          pht(
+            'Absolute TTL must be in the present or future, but TTL "%s" '.
+            'is in the past.',
+            $absolute_ttl));
+      }
+
+      $this->setTtl($absolute_ttl);
+    } else if ($relative_ttl !== null) {
+      if ($relative_ttl < 0) {
+        throw new Exception(
+          pht(
+            'Relative TTL must be zero or more seconds, but "%s" is '.
+            'negative.',
+            $relative_ttl));
+      }
+
+      $max_relative = phutil_units('365 days in seconds');
+      if ($relative_ttl > $max_relative) {
+        throw new Exception(
+          pht(
+            'Relative TTL must not be more than "%s" seconds, but TTL '.
+            '"%s" was specified.',
+            $max_relative,
+            $relative_ttl));
+      }
+
+      $absolute_ttl = PhabricatorTime::getNow() + $relative_ttl;
+
+      $this->setTtl($absolute_ttl);
+    }
 
     $view_policy = idx($params, 'viewPolicy');
     if ($view_policy) {
diff --git a/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php b/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
--- a/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
+++ b/src/applications/files/storage/__tests__/PhabricatorFileTestCase.php
@@ -370,11 +370,11 @@
 
     $data = Filesystem::readRandomCharacters(64);
 
-    $ttl = (time() + 60 * 60 * 24);
+    $ttl = (PhabricatorTime::getNow() + phutil_units('24 hours in seconds'));
 
     $params = array(
       'name' => 'test.dat',
-      'ttl'  => ($ttl),
+      'ttl.absolute' => $ttl,
       'storageEngines' => array(
         $engine,
       ),
diff --git a/src/applications/files/uploadsource/PhabricatorFileUploadSource.php b/src/applications/files/uploadsource/PhabricatorFileUploadSource.php
--- a/src/applications/files/uploadsource/PhabricatorFileUploadSource.php
+++ b/src/applications/files/uploadsource/PhabricatorFileUploadSource.php
@@ -4,7 +4,7 @@
   extends Phobject {
 
   private $name;
-  private $ttl;
+  private $relativeTTL;
   private $viewPolicy;
 
   private $rope;
@@ -22,13 +22,13 @@
     return $this->name;
   }
 
-  public function setTTL($ttl) {
-    $this->ttl = $ttl;
+  public function setRelativeTTL($relative_ttl) {
+    $this->relativeTTL = $relative_ttl;
     return $this;
   }
 
-  public function getTTL() {
-    return $this->ttl;
+  public function getRelativeTTL() {
+    return $this->relativeTTL;
   }
 
   public function setViewPolicy($view_policy) {
@@ -214,7 +214,7 @@
   private function getNewFileParameters() {
     return array(
       'name' => $this->getName(),
-      'ttl' => $this->getTTL(),
+      'ttl.relative' => $this->getRelativeTTL(),
       'viewPolicy' => $this->getViewPolicy(),
     );
   }
diff --git a/src/applications/phragment/conduit/PhragmentGetPatchConduitAPIMethod.php b/src/applications/phragment/conduit/PhragmentGetPatchConduitAPIMethod.php
--- a/src/applications/phragment/conduit/PhragmentGetPatchConduitAPIMethod.php
+++ b/src/applications/phragment/conduit/PhragmentGetPatchConduitAPIMethod.php
@@ -178,7 +178,7 @@
         $data,
         array(
           'name' => 'patch.dmp',
-          'ttl' => time() + 60 * 60 * 24,
+          'ttl.relative' => phutil_units('24 hours in seconds'),
         ));
       $patches[$key]['patchURI'] = $file->getDownloadURI();
     }
diff --git a/src/applications/phragment/controller/PhragmentPatchController.php b/src/applications/phragment/controller/PhragmentPatchController.php
--- a/src/applications/phragment/controller/PhragmentPatchController.php
+++ b/src/applications/phragment/controller/PhragmentPatchController.php
@@ -83,7 +83,7 @@
       array(
         'name' => $name,
         'mime-type' => 'text/plain',
-        'ttl' => time() + 60 * 60 * 24,
+        'ttl.relative' => phutil_units('24 hours in seconds'),
       ));
 
     $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
diff --git a/src/applications/phragment/controller/PhragmentZIPController.php b/src/applications/phragment/controller/PhragmentZIPController.php
--- a/src/applications/phragment/controller/PhragmentZIPController.php
+++ b/src/applications/phragment/controller/PhragmentZIPController.php
@@ -104,7 +104,7 @@
       $data,
       array(
         'name' => $zip_name,
-        'ttl' => time() + 60 * 60 * 24,
+        'ttl.relative' => phutil_units('24 hours in seconds'),
       ));
 
     $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();