diff --git a/package.json b/package.json
index 5a5282c..a070008 100644
--- a/package.json
+++ b/package.json
@@ -36,6 +36,7 @@
     "rollup-watch": "^2.5.0"
   },
   "dependencies": {
+    "d3-time-format": "^2.0.3",
     "mustache": "^2.3.0"
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 9ce83bb..fa9e73e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -331,6 +331,16 @@ cssom@0.3.x, "cssom@>= 0.3.0 < 0.4.0":
   dependencies:
     cssom "0.3.x"
 
+d3-time-format@^2.0.3:
+  version "2.0.3"
+  resolved "https://registry.yarnpkg.com/d3-time-format/-/d3-time-format-2.0.3.tgz#3241569b74ddc9c42e0689c0e8a903579fd6280a"
+  dependencies:
+    d3-time "1"
+
+d3-time@1:
+  version "1.0.4"
+  resolved "https://registry.yarnpkg.com/d3-time/-/d3-time-1.0.4.tgz#2ceba09a76b7450c992a1ded4e10fc6195e69649"
+
 dashdash@^1.12.0:
   version "1.14.1"
   resolved "https://registry.yarnpkg.com/dashdash/-/dashdash-1.14.1.tgz#853cfa0f7cbe2fed5de20326b8dd581035f6e2f0"