diff --git a/day_3/README.md b/day_3/README.md
index e07ba6f..463fe43 100644
--- a/day_3/README.md
+++ b/day_3/README.md
@@ -1,4 +1,4 @@
-# day 1
+# day 3
 
 ## Instructions
 
diff --git a/day_4/README.md b/day_4/README.md
index e69de29..bc833c4 100644
--- a/day_4/README.md
+++ b/day_4/README.md
@@ -0,0 +1,71 @@
+# day 4
+
+## Instructions
+
+- setup project
+- clone to your github
+- Read the documentation https://sequelize.org/v7/manual/getting-started.html
+- Setup the following Models in models folder. Make sure tables made by sequelize:
+
+```
+email
+- id
+- slug (unique)
+- subject
+- body
+- status ENUM(active, inactive) (integer mapping)
+
+email_queue
+- id
+- email_id
+- user_id
+- status ENUM(send, not sent) (integer mapping)
+- created_at
+- send_at
+- updated_at
+
+user
+- id
+- email
+- name
+- status ENUM(active, inactive) (integer mapping)
+```
+
+- Make the CRUD API for these tables
+
+```
+GET /api/v1/email (get all)
+GET /api/v1/email/:id (get one)
+POST /api/v1/email/:id (add one)
+PUT /api/v1/email/:id (update one)
+DELETE /api/v1/email/:id (delete one)
+
+GET /api/v1/user (get all)
+GET /api/v1/user/:id (get one)
+POST /api/v1/user/:id (add one)
+PUT /api/v1/user/:id (update one)
+DELETE /api/v1/user/:id (delete one)
+```
+
+- create a cronjob called email_queue.js in cronjob folder
+- this cronjob will be run once a day
+- Algorithm:
+
+```
+1.Loop through all active users
+2.Loop through all odd id emails if today is monday, wednesday, friday. Otherwise do all even id for other days.
+3.Write into email queue what email to send from step 2. Set status as not sent. Set send_at as next day.
+```
+
+- create a cronjob called email_sending.js in cronjob folder
+- this cronjob will be run once a day
+- Algorithm:
+
+```
+1.Loop through all email_queue table that have send_at as today.
+2.Query user table to collect email and name. In email template selected, replace {{{NAME}}} and {{{EMAIL}}} with user email and name.
+3.Send email to user. Use https://mailtrap.io/ to send the email
+4.Mark Email status as sent
+```
+
+- Everything must be done by end of date
diff --git a/day_4/app.js b/day_4/app.js
new file mode 100644
index 0000000..97a1728
--- /dev/null
+++ b/day_4/app.js
@@ -0,0 +1,44 @@
+var createError = require('http-errors');
+var express = require('express');
+var path = require('path');
+var cookieParser = require('cookie-parser');
+var logger = require('morgan');
+
+var indexRouter = require('./routes/index');
+var usersRouter = require('./routes/users');
+
+const db = require("./models");
+var cors = require("cors");
+
+var app = express();
+app.set("db", db);
+// view engine setup
+app.set('views', path.join(__dirname, 'views'));
+app.set('view engine', 'jade');
+app.use(cors());
+app.use(logger('dev'));
+app.use(express.json());
+app.use(express.urlencoded({ extended: false }));
+app.use(cookieParser());
+app.use(express.static(path.join(__dirname, 'public')));
+
+app.use('/', indexRouter);
+app.use('/users', usersRouter);
+
+// catch 404 and forward to error handler
+app.use(function (req, res, next) {
+  next(createError(404));
+});
+
+// error handler
+app.use(function (err, req, res, next) {
+  // set locals, only providing error in development
+  res.locals.message = err.message;
+  res.locals.error = req.app.get('env') === 'development' ? err : {};
+
+  // render the error page
+  res.status(err.status || 500);
+  res.render('error');
+});
+
+module.exports = app;
diff --git a/day_4/bin/www b/day_4/bin/www
new file mode 100755
index 0000000..cd1a62f
--- /dev/null
+++ b/day_4/bin/www
@@ -0,0 +1,90 @@
+#!/usr/bin/env node
+
+/**
+ * Module dependencies.
+ */
+
+var app = require('../app');
+var debug = require('debug')('day-1:server');
+var http = require('http');
+
+/**
+ * Get port from environment and store in Express.
+ */
+
+var port = normalizePort(process.env.PORT || '3000');
+app.set('port', port);
+
+/**
+ * Create HTTP server.
+ */
+
+var server = http.createServer(app);
+
+/**
+ * Listen on provided port, on all network interfaces.
+ */
+
+server.listen(port);
+server.on('error', onError);
+server.on('listening', onListening);
+
+/**
+ * Normalize a port into a number, string, or false.
+ */
+
+function normalizePort(val) {
+  var port = parseInt(val, 10);
+
+  if (isNaN(port)) {
+    // named pipe
+    return val;
+  }
+
+  if (port >= 0) {
+    // port number
+    return port;
+  }
+
+  return false;
+}
+
+/**
+ * Event listener for HTTP server "error" event.
+ */
+
+function onError(error) {
+  if (error.syscall !== 'listen') {
+    throw error;
+  }
+
+  var bind = typeof port === 'string'
+    ? 'Pipe ' + port
+    : 'Port ' + port;
+
+  // handle specific listen errors with friendly messages
+  switch (error.code) {
+    case 'EACCES':
+      console.error(bind + ' requires elevated privileges');
+      process.exit(1);
+      break;
+    case 'EADDRINUSE':
+      console.error(bind + ' is already in use');
+      process.exit(1);
+      break;
+    default:
+      throw error;
+  }
+}
+
+/**
+ * Event listener for HTTP server "listening" event.
+ */
+
+function onListening() {
+  var addr = server.address();
+  var bind = typeof addr === 'string'
+    ? 'pipe ' + addr
+    : 'port ' + addr.port;
+  debug('Listening on ' + bind);
+}
diff --git a/day_4/cronjobs/example.js b/day_4/cronjobs/example.js
new file mode 100644
index 0000000..5cb37f5
--- /dev/null
+++ b/day_4/cronjobs/example.js
@@ -0,0 +1,5 @@
+const db = require('../models');
+
+(async function tokenCronJob() {
+  await db.query('UPDATE `token` SET status=0 WHERE `expire_at` < NOW();');
+})();
\ No newline at end of file
diff --git a/day_4/models/index.js b/day_4/models/index.js
new file mode 100644
index 0000000..39f447f
--- /dev/null
+++ b/day_4/models/index.js
@@ -0,0 +1,68 @@
+'use strict';
+/*Powered By: Manaknightdigital Inc. https://manaknightdigital.com/ Year: 2020*/
+/**
+ * Sequelize File
+ * @copyright 2020 Manaknightdigital Inc.
+ * @link https://manaknightdigital.com
+ * @license Proprietary Software licensing
+ * @author Ryan Wong
+ *
+ */
+const fs = require('fs');
+const path = require('path');
+let Sequelize = require('sequelize');
+const basename = path.basename(__filename);
+const config = {
+  DB_DATABASE: 'mysql',
+  DB_USERNAME: 'root',
+  DB_PASSWORD: 'root',
+  DB_ADAPTER: 'mysql',
+  DB_NAME: 'day_1',
+  DB_HOSTNAME: 'localhost',
+  DB_PORT: 3306,
+};
+
+let db = {};
+
+let sequelize = new Sequelize(config.DB_DATABASE, config.DB_USERNAME, config.DB_PASSWORD, {
+  dialect: config.DB_ADAPTER,
+  username: config.DB_USERNAME,
+  password: config.DB_PASSWORD,
+  database: config.DB_NAME,
+  host: config.DB_HOSTNAME,
+  port: config.DB_PORT,
+  logging: console.log,
+  timezone: '-04:00',
+  pool: {
+    maxConnections: 1,
+    minConnections: 0,
+    maxIdleTime: 100,
+  },
+  define: {
+    timestamps: false,
+    underscoredAll: true,
+    underscored: true,
+  },
+});
+
+// sequelize.sync({ force: true });
+
+fs.readdirSync(__dirname)
+  .filter((file) => {
+    return file.indexOf('.') !== 0 && file !== basename && file.slice(-3) === '.js';
+  })
+  .forEach((file) => {
+    var model = sequelize['import'](path.join(__dirname, file));
+    db[model.name] = model;
+  });
+
+Object.keys(db).forEach((modelName) => {
+  if (db[modelName].associate) {
+    db[modelName].associate(db);
+  }
+});
+
+db.sequelize = sequelize;
+db.Sequelize = Sequelize;
+
+module.exports = db;
\ No newline at end of file
diff --git a/day_4/models/location.js b/day_4/models/location.js
new file mode 100644
index 0000000..7f430bb
--- /dev/null
+++ b/day_4/models/location.js
@@ -0,0 +1,26 @@
+module.exports = (sequelize, DataTypes) => {
+  const location = sequelize.define(
+    "location",
+    {
+      id: {
+        type: DataTypes.INTEGER,
+        primaryKey: true,
+        autoIncrement: true,
+      },
+      name: DataTypes.STRING,
+      created_at: DataTypes.DATEONLY,
+      updated_at: DataTypes.DATE,
+    },
+    {
+      timestamps: true,
+      freezeTableName: true,
+      tableName: "location",
+    },
+    {
+      underscoredAll: false,
+      underscored: false,
+    }
+  );
+
+  return location;
+};
\ No newline at end of file
diff --git a/day_4/package.json b/day_4/package.json
new file mode 100644
index 0000000..219c20e
--- /dev/null
+++ b/day_4/package.json
@@ -0,0 +1,19 @@
+{
+  "name": "day-1",
+  "version": "0.0.0",
+  "private": true,
+  "scripts": {
+    "start": "node ./bin/www"
+  },
+  "dependencies": {
+    "cookie-parser": "~1.4.4",
+    "cors": "^2.8.5",
+    "debug": "~2.6.9",
+    "express": "~4.16.1",
+    "http-errors": "~1.6.3",
+    "jade": "~1.11.0",
+    "morgan": "~1.9.1",
+    "mysql2": "^2.3.3",
+    "sequelize": "^6.15.1"
+  }
+}
diff --git a/day_4/public/stylesheets/style.css b/day_4/public/stylesheets/style.css
new file mode 100644
index 0000000..9453385
--- /dev/null
+++ b/day_4/public/stylesheets/style.css
@@ -0,0 +1,8 @@
+body {
+  padding: 50px;
+  font: 14px "Lucida Grande", Helvetica, Arial, sans-serif;
+}
+
+a {
+  color: #00B7FF;
+}
diff --git a/day_4/routes/index.js b/day_4/routes/index.js
new file mode 100644
index 0000000..ecca96a
--- /dev/null
+++ b/day_4/routes/index.js
@@ -0,0 +1,9 @@
+var express = require('express');
+var router = express.Router();
+
+/* GET home page. */
+router.get('/', function(req, res, next) {
+  res.render('index', { title: 'Express' });
+});
+
+module.exports = router;
diff --git a/day_4/routes/users.js b/day_4/routes/users.js
new file mode 100644
index 0000000..623e430
--- /dev/null
+++ b/day_4/routes/users.js
@@ -0,0 +1,9 @@
+var express = require('express');
+var router = express.Router();
+
+/* GET users listing. */
+router.get('/', function(req, res, next) {
+  res.send('respond with a resource');
+});
+
+module.exports = router;
diff --git a/day_4/views/error.jade b/day_4/views/error.jade
new file mode 100644
index 0000000..51ec12c
--- /dev/null
+++ b/day_4/views/error.jade
@@ -0,0 +1,6 @@
+extends layout
+
+block content
+  h1= message
+  h2= error.status
+  pre #{error.stack}
diff --git a/day_4/views/index.jade b/day_4/views/index.jade
new file mode 100644
index 0000000..3d63b9a
--- /dev/null
+++ b/day_4/views/index.jade
@@ -0,0 +1,5 @@
+extends layout
+
+block content
+  h1= title
+  p Welcome to #{title}
diff --git a/day_4/views/layout.jade b/day_4/views/layout.jade
new file mode 100644
index 0000000..15af079
--- /dev/null
+++ b/day_4/views/layout.jade
@@ -0,0 +1,7 @@
+doctype html
+html
+  head
+    title= title
+    link(rel='stylesheet', href='/stylesheets/style.css')
+  body
+    block content