diff --git a/debian/changelog b/debian/changelog
index 5713a81..51daae8 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,15 @@
+base-files (10.3+mendel1) mendel-day; urgency=medium
+
+  * Bump for the Day 4.0 release
+  * Mirror changes to upstream base-files:
+  - Remove VERSION and VERSION_ID from release.
+  - Add CC0-1.0 to common-licenses.
+  - Add Breaks: debian-security-support.
+  - Add VERSION_CODENAME to os-release.
+  - Update Standards-Version to 4.1.3.
+
+ -- Coral <coral-support@google.com>  Tue, 20 Aug 2019 13:40:57 -0700
+
 base-files (9.9+mendel6) mendel-chef; urgency=medium
 
   * Bump for the Chef 3.1 point release
diff --git a/debian/control b/debian/control
index 678aea3..378a335 100644
--- a/debian/control
+++ b/debian/control
@@ -2,7 +2,7 @@
 Section: admin
 Priority: required
 Maintainer: Coral <coral-support@google.com>
-Standards-Version: 3.9.8
+Standards-Version: 4.1.3
 Build-Depends: debhelper (>= 9)
 
 Package: base-files
@@ -13,7 +13,8 @@
 Essential: yes
 Priority: required
 Replaces: base, miscutils, dpkg (<= 1.15.0)
-Breaks: initscripts (<< 2.88dsf-13.3), sendfile (<< 2.1b.20080616-5.2~)
+Breaks: initscripts (<< 2.88dsf-13.3), sendfile (<< 2.1b.20080616-5.2~),
+ debian-security-support (<< 2019.04.25)
 Multi-Arch: foreign
 Description: Mendel base system miscellaneous files
  This package contains the basic filesystem hierarchy of a Mendel system, and
diff --git a/etc/debian_version b/etc/debian_version
index 9d5e716..2f52450 100644
--- a/etc/debian_version
+++ b/etc/debian_version
@@ -1 +1 @@
-9.7
+10.0
diff --git a/etc/issue b/etc/issue
index 6c3dc4f..0d266a6 100644
--- a/etc/issue
+++ b/etc/issue
@@ -1,2 +1,2 @@
-Mendel #OSNAME# (chef) \n \l
+Mendel #OSNAME# (day) \n \l
 
diff --git a/etc/issue.net b/etc/issue.net
index ee883f8..083a488 100644
--- a/etc/issue.net
+++ b/etc/issue.net
@@ -1 +1 @@
-Mendel #OSNAME# (chef)
+Mendel #OSNAME# (day)
diff --git a/etc/lsb-release b/etc/lsb-release
index 6c17bc9..533f2a7 100644
--- a/etc/lsb-release
+++ b/etc/lsb-release
@@ -1,7 +1,7 @@
-DISTRIB_CODENAME=chef
-DISTRIB_DESCRIPTION="Mendel GNU/Linux Chef"
+DISTRIB_CODENAME=day
+DISTRIB_DESCRIPTION="Mendel GNU/Linux Day"
 DISTRIB_ID=Mendel
-DISTRIB_RELEASE=mendel-chef
+DISTRIB_RELEASE=mendel-day
 PRETTY_NAME="Mendel"
 NAME="Mendel"
 ID=Mendel
diff --git a/etc/mendel_version b/etc/mendel_version
index 8c50098..5186d07 100644
--- a/etc/mendel_version
+++ b/etc/mendel_version
@@ -1 +1 @@
-3.1
+4.0
diff --git a/etc/os-release b/etc/os-release
index e91dfcc..d052fbf 100644
--- a/etc/os-release
+++ b/etc/os-release
@@ -1,9 +1,8 @@
-PRETTY_NAME="Mendel #OSNAME# 3 (Chef)"
+PRETTY_NAME="Mendel #OSNAME# 4 (Day)"
 NAME="Mendel #OSNAME#"
-VERSION_ID="3"
-VERSION="3 (chef)"
 ID=mendel
 ID_LIKE=debian
 HOME_URL="https://coral.withgoogle.com/"
 SUPPORT_URL="https://coral.withgoogle.com/"
 BUG_REPORT_URL="https://coral.withgoogle.com/"
+VERSION_CODENAME="day"
diff --git a/licenses/CC0-1.0 b/licenses/CC0-1.0
new file mode 100644
index 0000000..0e259d4
--- /dev/null
+++ b/licenses/CC0-1.0
@@ -0,0 +1,121 @@
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