How to prevent Sequelize from converting Date object to local time

When using ORM tools like Sequelize, it automatically handles JavaScript Date objects, converting them to database-supported formats. During this process, Sequelize typically converts Date objects to local time, which may result in inconsistent or incorrect time across servers in different geographical locations.

To prevent Sequelize from converting Date objects to local time, you can use the following methods:

1. Using UTC Time

A common approach is to configure Sequelize to use UTC time instead of local time. This ensures consistent time storage regardless of server location. Set this configuration when initializing Sequelize:

javascript
const sequelize = new Sequelize('database', 'username', 'password', {
  host: 'host',
  dialect: 'mysql', // or other database dialect
  dialectOptions: {
    useUTC: true, // For MySQL, set this to true
    dateStrings: true,
    typeCast: true
  },
  timezone: '+00:00' // Set timezone to UTC
});

2. Using Strings Instead of Date Objects

If you need full control over date and time formatting, handle date and time at the application level. Store date and time as strings (e.g., in ISO 8601 format) to avoid unnecessary conversions by Sequelize or the database.

In your model, define it as follows:

javascript
module.exports = (sequelize, DataTypes) => {
  return sequelize.define('Model', {
    // Define a string field instead of a date field
    dateString: {
      type: DataTypes.STRING,
      allowNull: false
    }
  });
};

Manually convert Date objects to strings when inserting or querying data:

javascript
const moment = require('moment');

// Create a record
Model.create({
  dateString: moment(new Date()).utc().format()
});

// Convert back to Date object when querying
Model.findOne({ where: { id: 1 } }).then(record => {
  const date = new Date(record.dateString);
});

3. Time Zone Conversion

If you need to handle multiple time zones within your application while keeping the database using UTC time, perform time zone conversions at the application level. Use libraries like moment-timezone for these conversions:

javascript
const moment = require('moment-timezone');

// Convert UTC time to Tokyo time
const timeInTokyo = moment.utc(dateFromDatabase).tz('Asia/Tokyo').format();

By implementing these methods, you can control how Sequelize handles Date objects and avoid issues from unnecessary time zone conversions. This is particularly important for applications spanning geographical locations, ensuring data consistency and accuracy.