diff --git a/.circleci/config.yml b/.circleci/config.yml
index 6438ac0..8b8a9d4 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -9,11 +9,11 @@ jobs:
 
       - restore_cache:
           keys:
-          - deps-{{ checksum "bower.json" }}-{{ checksum "package.json" }}
+          - deps-{{ checksum "packages.dhall" }}-{{ checksum "package.json" }}
 
       - run:
           command: |
-            yarn add --dev bower purescript pulp
+            yarn add --dev purescript spago
             yarn
             yarn build
             git checkout -- package.json
@@ -23,7 +23,7 @@ jobs:
             - node_modules
             - bower_components
             - output
-          key: deps-{{ checksum "bower.json" }}-{{ checksum "package.json" }}
+          key: deps-{{ checksum "packages.dhall" }}-{{ checksum "package.json" }}
 
       - run:
           command: yarn jest
diff --git a/.gitignore b/.gitignore
index f42738e..8903044 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,4 +4,6 @@ yarn.lock
 
 .psc-ide-port
 .psci_modules
+.purs-repl
+.spago
 output
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..31e33c0
--- /dev/null
+++ b/README.md
@@ -0,0 +1,11 @@
+# purescript-nonbili
+
+Prelude and helper modules shared by nonbili packages.
+
+## Development
+
+```
+yarn
+spago build -w
+yarn jest
+```
diff --git a/bower.json b/bower.json
deleted file mode 100644
index cd9d69d..0000000
--- a/bower.json
+++ /dev/null
@@ -1,38 +0,0 @@
-{
-  "name": "purescript-nonbili",
-  "description": "Some shared purescript modules used at Nonbili",
-  "authors": [
-    "Ping Chen <remotenonsense@gmail.com>"
-  ],
-  "repository": {
-    "type": "git",
-    "url": "git://github.com/nonbili/purescript-nonbili.git"
-  },
-  "license": "BSD-3-Clause",
-  "ignore": [
-    "**/.*",
-    "node_modules",
-    "bower_components",
-    "output"
-  ],
-  "dependencies": {
-    "purescript-prelude": "^4.1.0",
-    "purescript-effect": "^2.0.1",
-    "purescript-debug": "^4.0.0",
-    "purescript-tuples": "^5.1.0",
-    "purescript-either": "^4.1.1",
-    "purescript-arrays": "^5.2.0",
-    "purescript-call-by-name": "^2.0.0",
-    "purescript-const": "^4.1.0",
-    "purescript-transformers": "^4.1.0",
-    "purescript-strings": "^4.0.1",
-    "purescript-js-date": "^6.0.0",
-    "purescript-argonaut-codecs": "^6.0.2",
-    "purescript-aff": "^5.1.2"
-  },
-  "devDependencies": {
-    "purescript-quickcheck": "^6.1.0",
-    "purescript-jest": "^0.2.0",
-    "purescript-psci-support": "^4.0.0"
-  }
-}
diff --git a/package.json b/package.json
index 6d5e298..c488e9b 100644
--- a/package.json
+++ b/package.json
@@ -2,9 +2,8 @@
   "private": true,
   "license": "BSD-3-Clause",
   "scripts": {
-    "build": "pulp build -I test -- +RTS -N2 -RTS",
-    "postinstall": "bower install",
-    "test": "pulp build -I test && jest"
+    "build": "spago build -u '+RTS -N2 -RTS'",
+    "test": "spago build && jest"
   },
   "devDependencies": {
     "jest": "^24.0.0"
diff --git a/packages.dhall b/packages.dhall
new file mode 100644
index 0000000..680dede
--- /dev/null
+++ b/packages.dhall
@@ -0,0 +1,7 @@
+let upstream =
+      https://github.com/purescript/package-sets/releases/download/psc-0.13.8-20200831/packages.dhall sha256:cdb3529cac2cd8dd780f07c80fd907d5faceae7decfcaa11a12037df68812c83
+
+let nonbili =
+      https://github.com/nonbili/package-sets/releases/download/v0.7/packages.dhall sha256:b09c8d62a7a1e04fd150d32d80f575c0f1e6d82f2dc2a763eb4271cdb61a154d
+
+in  upstream // nonbili
diff --git a/spago.dhall b/spago.dhall
new file mode 100644
index 0000000..c114534
--- /dev/null
+++ b/spago.dhall
@@ -0,0 +1,27 @@
+{-
+Welcome to a Spago project!
+You can edit this file as you like.
+-}
+{ name = "nonbili"
+, dependencies =
+  [ "aff"
+  , "argonaut-codecs"
+  , "arrays"
+  , "call-by-name"
+  , "console"
+  , "const"
+  , "debug"
+  , "effect"
+  , "either"
+  , "jest"
+  , "js-date"
+  , "prelude"
+  , "psci-support"
+  , "quickcheck"
+  , "strings"
+  , "transformers"
+  , "tuples"
+  ]
+, packages = ./packages.dhall
+, sources = [ "src/**/*.purs", "test/**/*.purs" ]
+}
diff --git a/src/Nonbili/DateTime.purs b/src/Nonbili/DateTime.purs
index ef1c26c..fba715b 100644
--- a/src/Nonbili/DateTime.purs
+++ b/src/Nonbili/DateTime.purs
@@ -11,7 +11,7 @@ module Nonbili.DateTime
 import Nonbili.Prelude
 
 import Data.Argonaut.Core as A
-import Data.Argonaut.Decode (class DecodeJson)
+import Data.Argonaut.Decode (class DecodeJson, JsonDecodeError(..))
 import Data.Argonaut.Encode (class EncodeJson)
 import Data.JSDate (JSDate)
 import Data.JSDate as JSDate
@@ -23,7 +23,7 @@ derive instance ordDateTime :: Ord DateTime
 
 instance decodeJsonDateTime :: DecodeJson DateTime where
   decodeJson json =
-    note "Invalid date" $ (A.toString json >>= read)
+    note (UnexpectedValue json) $ (A.toString json >>= read)
 
 instance encodeJsonDateTime :: EncodeJson DateTime where
   encodeJson (DateTime date) =
diff --git a/test/Nonbili/String.purs b/test/Nonbili/String.purs
index 2c4c0b7..9b8b99a 100644
--- a/test/Nonbili/String.purs
+++ b/test/Nonbili/String.purs
@@ -15,7 +15,7 @@ spec :: Effect Unit
 spec = do
   test "padStart" $ do
     let re = unsafeRegex "^0+$" RegexFlags.noFlags
-    quickCheck \n s -> do
+    liftEffect $ quickCheck \n s -> do
       let
         lengthDiff = n - String.length s
         { before, after } = String.splitAt lengthDiff $ padStart n s