diff --git a/base/build_time.cc b/base/build_time.cc
deleted file mode 100644
index 834b041..0000000
--- a/base/build_time.cc
+++ /dev/null
@@ -1,25 +0,0 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "base/build_time.h"
-
-// Imports the generated build date, i.e. BUILD_DATE.
-#include "base/generated_build_date.h"
-
-#include "base/logging.h"
-#include "base/time/time.h"
-
-namespace base {
-
-Time GetBuildTime() {
-  Time integral_build_time;
-  // BUILD_DATE is exactly "Mmm DD YYYY HH:MM:SS".
-  // See //build/write_build_date_header.py. "HH:MM:SS" is normally expected to
-  // be "05:00:00" but is not enforced here.
-  bool result = Time::FromUTCString(BUILD_DATE, &integral_build_time);
-  DCHECK(result);
-  return integral_build_time;
-}
-
-}  // namespace base
diff --git a/base/build_time.h b/base/build_time.h
deleted file mode 100644
index 83c9875..0000000
--- a/base/build_time.h
+++ /dev/null
@@ -1,30 +0,0 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef BASE_BUILD_TIME_H_
-#define BASE_BUILD_TIME_H_
-
-#include "base/base_export.h"
-#include "base/time/time.h"
-
-namespace base {
-
-// GetBuildTime returns the time at which the current binary was built,
-// rounded down to 5:00:00am at the start of the day in UTC.
-//
-// This uses a generated file, which doesn't trigger a rebuild when the time
-// changes. It will, however, be updated whenever //build/util/LASTCHANGE
-// changes.
-//
-// This value should only be considered accurate to within a day.
-// It will always be in the past.
-//
-// Note: If the build is not official (i.e. is_official_build = false)
-// this time will be set to 5:00:00am on the most recent first Sunday
-// of a month.
-Time BASE_EXPORT GetBuildTime();
-
-}  // namespace base
-
-#endif  // BASE_BUILD_TIME_H_
diff --git a/base/build_time_unittest.cc b/base/build_time_unittest.cc
deleted file mode 100644
index 3a35736..0000000
--- a/base/build_time_unittest.cc
+++ /dev/null
@@ -1,37 +0,0 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "base/build_time.h"
-#include "base/generated_build_date.h"
-#include "base/time/time.h"
-
-#include "testing/gtest/include/gtest/gtest.h"
-
-TEST(BuildTime, DateLooksValid) {
-  char build_date[] = BUILD_DATE;
-
-  EXPECT_EQ(20u, strlen(build_date));
-  EXPECT_EQ(' ', build_date[3]);
-  EXPECT_EQ(' ', build_date[6]);
-  EXPECT_EQ(' ', build_date[11]);
-  EXPECT_EQ('0', build_date[12]);
-  EXPECT_EQ('5', build_date[13]);
-  EXPECT_EQ(':', build_date[14]);
-  EXPECT_EQ('0', build_date[15]);
-  EXPECT_EQ('0', build_date[16]);
-  EXPECT_EQ(':', build_date[17]);
-  EXPECT_EQ('0', build_date[18]);
-  EXPECT_EQ('0', build_date[19]);
-}
-
-TEST(BuildTime, InThePast) {
-  EXPECT_LT(base::GetBuildTime(), base::Time::Now());
-  EXPECT_LT(base::GetBuildTime(), base::Time::NowFromSystemTime());
-}
-
-TEST(BuildTime, NotTooFar) {
-  // BuildTime must be less than 45 days old.
-  base::Time cutoff(base::Time::Now() - base::TimeDelta::FromDays(45));
-  EXPECT_GT(base::GetBuildTime(), cutoff);
-}
diff --git a/base/metrics/field_trial.cc b/base/metrics/field_trial.cc
index ff37880..ed4f147 100644
--- a/base/metrics/field_trial.cc
+++ b/base/metrics/field_trial.cc
@@ -8,7 +8,6 @@
 #include <utility>
 
 #include "base/base_switches.h"
-#include "base/build_time.h"
 #include "base/command_line.h"
 #include "base/debug/activity_tracker.h"
 #include "base/logging.h"
@@ -500,10 +499,7 @@
   DCHECK(!used_without_global_);
   global_ = this;
 
-  Time two_years_from_build_time = GetBuildTime() + TimeDelta::FromDays(730);
-  Time::Exploded exploded;
-  two_years_from_build_time.LocalExplode(&exploded);
-  kNoExpirationYear = exploded.year;
+  CHECK(false);  // TODO(scottmg): Remove FieldTrialList.
 }
 
 FieldTrialList::~FieldTrialList() {
@@ -592,9 +588,7 @@
 
   FieldTrial* field_trial = new FieldTrial(trial_name, total_probability,
                                            default_group_name, entropy_value);
-  if (GetBuildTime() > CreateTimeFromParams(year, month, day_of_month))
-    field_trial->Disable();
-  FieldTrialList::Register(field_trial);
+  CHECK(false);  // TODO(scottmg): Remove FieldTrialList.
   return field_trial;
 }
 
diff --git a/base/metrics/field_trial_unittest.cc b/base/metrics/field_trial_unittest.cc
index 3f7cc30..41550dd 100644
--- a/base/metrics/field_trial_unittest.cc
+++ b/base/metrics/field_trial_unittest.cc
@@ -7,7 +7,6 @@
 #include <stddef.h>
 
 #include "base/base_switches.h"
-#include "base/build_time.h"
 #include "base/feature_list.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
@@ -43,13 +42,6 @@
       default_group_number);
 }
 
-int OneYearBeforeBuildTime() {
-  Time one_year_before_build_time = GetBuildTime() - TimeDelta::FromDays(365);
-  Time::Exploded exploded;
-  one_year_before_build_time.LocalExplode(&exploded);
-  return exploded.year;
-}
-
 // FieldTrialList::Observer implementation for testing.
 class TestFieldTrialObserver : public FieldTrialList::Observer {
  public:
@@ -273,26 +265,6 @@
   EXPECT_EQ(trial->group_name(), winner_name);
 }
 
-TEST_F(FieldTrialTest, DisableProbability) {
-  const std::string default_group_name = "Default group";
-  const std::string loser = "Loser";
-  const std::string name = "Trial";
-
-  // Create a field trail that has expired.
-  int default_group_number = -1;
-  FieldTrial* trial = FieldTrialList::FactoryGetFieldTrial(
-      name, 1000000000, default_group_name, OneYearBeforeBuildTime(), 1, 1,
-      FieldTrial::SESSION_RANDOMIZED,
-      &default_group_number);
-  trial->AppendGroup(loser, 999999999);  // 99.9999999% chance of being chosen.
-
-  // Because trial has expired, we should always be in the default group.
-  EXPECT_EQ(default_group_number, trial->group());
-
-  // And that default_group_name should ALWAYS win.
-  EXPECT_EQ(default_group_name, trial->group_name());
-}
-
 TEST_F(FieldTrialTest, ActiveGroups) {
   std::string no_group("No Group");
   scoped_refptr<FieldTrial> trial =
@@ -452,69 +424,6 @@
   EXPECT_EQ("Some name/Winner/xxx/yyyy/zzz/default/", save_string);
 }
 
-TEST_F(FieldTrialTest, SaveAll) {
-  std::string save_string;
-
-  scoped_refptr<FieldTrial> trial =
-      CreateFieldTrial("Some name", 10, "Default some name", nullptr);
-  EXPECT_EQ("", trial->group_name_internal());
-  FieldTrialList::AllStatesToString(&save_string, false);
-  EXPECT_EQ("Some name/Default some name/", save_string);
-  // Getting all states should have finalized the trial.
-  EXPECT_EQ("Default some name", trial->group_name_internal());
-  save_string.clear();
-
-  // Create a winning group.
-  trial = CreateFieldTrial("trial2", 10, "Default some name", nullptr);
-  trial->AppendGroup("Winner", 10);
-  // Finalize the group selection by accessing the selected group.
-  trial->group();
-  FieldTrialList::AllStatesToString(&save_string, false);
-  EXPECT_EQ("Some name/Default some name/*trial2/Winner/", save_string);
-  save_string.clear();
-
-  // Create a second trial and winning group.
-  scoped_refptr<FieldTrial> trial2 =
-      CreateFieldTrial("xxx", 10, "Default xxx", nullptr);
-  trial2->AppendGroup("yyyy", 10);
-  // Finalize the group selection by accessing the selected group.
-  trial2->group();
-
-  FieldTrialList::AllStatesToString(&save_string, false);
-  // We assume names are alphabetized... though this is not critical.
-  EXPECT_EQ("Some name/Default some name/*trial2/Winner/*xxx/yyyy/",
-            save_string);
-  save_string.clear();
-
-  // Create a third trial with only the default group.
-  scoped_refptr<FieldTrial> trial3 =
-      CreateFieldTrial("zzz", 10, "default", nullptr);
-
-  FieldTrialList::AllStatesToString(&save_string, false);
-  EXPECT_EQ("Some name/Default some name/*trial2/Winner/*xxx/yyyy/zzz/default/",
-            save_string);
-
-  // Create expired study.
-  int default_group_number = -1;
-  scoped_refptr<FieldTrial> expired_trial =
-      FieldTrialList::FactoryGetFieldTrial(
-          "Expired trial name", 1000000000, "Default group",
-          OneYearBeforeBuildTime(), 1, 1, FieldTrial::SESSION_RANDOMIZED,
-          &default_group_number);
-  expired_trial->AppendGroup("Expired trial group name", 999999999);
-
-  save_string.clear();
-  FieldTrialList::AllStatesToString(&save_string, false);
-  EXPECT_EQ("Some name/Default some name/*trial2/Winner/*xxx/yyyy/zzz/default/",
-            save_string);
-  save_string.clear();
-  FieldTrialList::AllStatesToString(&save_string, true);
-  EXPECT_EQ(
-      "Expired trial name/Default group/"
-      "Some name/Default some name/*trial2/Winner/*xxx/yyyy/zzz/default/",
-      save_string);
-}
-
 TEST_F(FieldTrialTest, Restore) {
   ASSERT_FALSE(FieldTrialList::TrialExists("Some_name"));
   ASSERT_FALSE(FieldTrialList::TrialExists("xxx"));
diff --git a/build/write_build_date_header.py b/build/write_build_date_header.py
deleted file mode 100755
index 6fe514f..0000000
--- a/build/write_build_date_header.py
+++ /dev/null
@@ -1,118 +0,0 @@
-#!/usr/bin/env python
-# Copyright (c) 2016 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-"""Writes a file that contains a define that approximates the build date.
-
-build_type impacts the timestamp generated:
-- default: the build date is set to the most recent first Sunday of a month at
-  5:00am. The reason is that it is a time where invalidating the build cache
-  shouldn't have major reprecussions (due to lower load).
-- official: the build date is set to the current date at 5:00am, or the day
-  before if the current time is before 5:00am.
-Either way, it is guaranteed to be in the past and always in UTC.
-
-It is also possible to explicitly set a build date to be used.
-"""
-
-import argparse
-import calendar
-import datetime
-import doctest
-import os
-import sys
-
-
-def GetFirstSundayOfMonth(year, month):
-  """Returns the first sunday of the given month of the given year.
-
-  >>> GetFirstSundayOfMonth(2016, 2)
-  7
-  >>> GetFirstSundayOfMonth(2016, 3)
-  6
-  >>> GetFirstSundayOfMonth(2000, 1)
-  2
-  """
-  weeks = calendar.Calendar().monthdays2calendar(year, month)
-  # Return the first day in the first week that is a Sunday.
-  return [date_day[0] for date_day in weeks[0] if date_day[1] == 6][0]
-
-
-def GetBuildDate(build_type, utc_now):
-  """Gets the approximate build date given the specific build type.
-
-  >>> GetBuildDate('default', datetime.datetime(2016, 2, 6, 1, 2, 3))
-  'Jan 03 2016 01:02:03'
-  >>> GetBuildDate('default', datetime.datetime(2016, 2, 7, 5))
-  'Feb 07 2016 05:00:00'
-  >>> GetBuildDate('default', datetime.datetime(2016, 2, 8, 5))
-  'Feb 07 2016 05:00:00'
-  """
-  day = utc_now.day
-  month = utc_now.month
-  year = utc_now.year
-  if build_type != 'official':
-    first_sunday = GetFirstSundayOfMonth(year, month)
-    # If our build is after the first Sunday, we've already refreshed our build
-    # cache on a quiet day, so just use that day.
-    # Otherwise, take the first Sunday of the previous month.
-    if day >= first_sunday:
-      day = first_sunday
-    else:
-      month -= 1
-      if month == 0:
-        month = 12
-        year -= 1
-      day = GetFirstSundayOfMonth(year, month)
-  now = datetime.datetime(
-      year, month, day, utc_now.hour, utc_now.minute, utc_now.second)
-  return '{:%b %d %Y %H:%M:%S}'.format(now)
-
-
-def main():
-  if doctest.testmod()[0]:
-    return 1
-  argument_parser = argparse.ArgumentParser(
-      description=sys.modules[__name__].__doc__,
-      formatter_class=argparse.RawDescriptionHelpFormatter)
-  argument_parser.add_argument('output_file', help='The file to write to')
-  argument_parser.add_argument(
-      'build_type', help='The type of build', choices=('official', 'default'))
-  argument_parser.add_argument(
-      'build_date_override', nargs='?',
-      help='Optional override for the build date. Format must be '
-           '\'Mmm DD YYYY HH:MM:SS\'')
-  args = argument_parser.parse_args()
-
-  if args.build_date_override:
-    # Format is expected to be "Mmm DD YYYY HH:MM:SS".
-    build_date = args.build_date_override
-  else:
-    now = datetime.datetime.utcnow()
-    if now.hour < 5:
-      # The time is locked at 5:00 am in UTC to cause the build cache
-      # invalidation to not happen exactly at midnight. Use the same calculation
-      # as the day before.
-      # See //base/build_time.cc.
-      now = now - datetime.timedelta(days=1)
-    now = datetime.datetime(now.year, now.month, now.day, 5, 0, 0)
-    build_date = GetBuildDate(args.build_type, now)
-
-  output = ('// Generated by //build/write_build_date_header.py\n'
-           '#ifndef BUILD_DATE\n'
-           '#define BUILD_DATE "{}"\n'
-           '#endif // BUILD_DATE\n'.format(build_date))
-
-  current_contents = ''
-  if os.path.isfile(args.output_file):
-    with open(args.output_file, 'r') as current_file:
-      current_contents = current_file.read()
-
-  if current_contents != output:
-    with open(args.output_file, 'w') as output_file:
-      output_file.write(output)
-  return 0
-
-
-if __name__ == '__main__':
-  sys.exit(main())
diff --git a/tools/gn/bootstrap/bootstrap.py b/tools/gn/bootstrap/bootstrap.py
index f2caac7..00bfa56 100755
--- a/tools/gn/bootstrap/bootstrap.py
+++ b/tools/gn/bootstrap/bootstrap.py
@@ -192,31 +192,10 @@
       os.path.join(SRC_ROOT, source),
   ])
 
-def write_build_date_header(root_gen_dir):
-  check_call([
-       sys.executable,
-       os.path.join(SRC_ROOT, 'build', 'write_build_date_header.py'),
-       os.path.join(root_gen_dir, 'base/generated_build_date.h'),
-       'default',
-  ])
-
 def build_gn_with_ninja_manually(tempdir, options, windows_x64_toolchain):
   root_gen_dir = os.path.join(tempdir, 'gen')
   mkdir_p(root_gen_dir)
 
-  write_build_date_header(root_gen_dir)
-
-  if is_mac:
-    # //base/build_time.cc needs base/generated_build_date.h,
-    # and this file is only included for Mac builds.
-    mkdir_p(os.path.join(root_gen_dir, 'base'))
-    check_call([
-        sys.executable,
-        os.path.join(SRC_ROOT, 'build', 'write_build_date_header.py'),
-        os.path.join(root_gen_dir, 'base', 'generated_build_date.h'),
-        'default'
-    ])
-
   if is_win:
     write_compiled_message(root_gen_dir,
         'base/trace_event/etw_manifest/chrome_events_win.man')
@@ -435,7 +414,6 @@
       'base/at_exit.cc',
       'base/base_paths.cc',
       'base/base_switches.cc',
-      'base/build_time.cc',
       'base/callback_helpers.cc',
       'base/callback_internal.cc',
       'base/command_line.cc',