How can I add timestamp to logs using Node.js library Winston?

I was dealing with the same issue myself. There are two ways I was able to do this.

When you include Winston, it usually defaults to adding a Console transport. In order to get timestamps to work in this default case, I needed to either:

1. Remove the console transport and add again with the timestamp option.
2. Create your own Logger object with the timestamp option set to true.

The first:

var winston = require('winston');
winston.remove(winston.transports.Console);
winston.add(winston.transports.Console, {'timestamp':true});

The second, and cleaner option:

var winston = require('winston');
var logger = new (winston.Logger)({
    transports: [
      new (winston.transports.Console)({'timestamp':true})
    ]
});

Some of the other options for Console transport can be found here:

• level: Level of messages that this transport should log (default 'debug').
• silent: Boolean flag indicating whether to suppress output (default false).
• colorize: Boolean flag indicating if we should colorize output (default false).
• timestamp: Boolean flag indicating if we should prepend output with timestamps (default false). If function is specified, its return value will be used instead of timestamps.

Above answers did not work for me. In case you are trying to add timestamp to your logs using the latest version of Winston - 3.0.0-rc1, this worked like charm:

    const {transports, createLogger, format} = require('winston');

    const logger = createLogger({
        format: format.combine(
            format.timestamp(),
            format.json()
        ),
        transports: [
            new transports.Console(),
            new transports.File({filename: 'logs/error/error.log', level: 'error'}),
            new transports.File({filename: 'logs/activity/activity.log', level:'info'})
        ]
    });

I used 'format.combine()'. Since I needed timestamp on all my transports, I added the formatting option within the createLogger, rather than inside each transport. My output on console and on file (activity.log) are as follows:

{"message":"Connected to mongodb","level":"info","timestamp":"2018-02-01T22:35:27.758Z"}
{"message":"Connected to mongodb","level":"info","timestamp":"2018-02-01T22:35:27.758Z"}

We can add formatting to this timestamp in 'format.combine()' as usual using:

format.timestamp({format:'MM-YY-DD'})

We can do like this also

var winston = require('winston');
const { createLogger, format, transports } = require('winston');
var config = require('../configurations/envconfig.js');

var loggerLevel = process.env.LOGGERLEVEL ||  config.get('LOGGERLEVEL');

var logger = winston.createLogger({
  format: format.combine(
    format.timestamp({
      format: 'YYYY-MM-DD HH:mm:ss'
    }),
    format.printf(info => `${info.timestamp} ${info.level}: ${info.message}`+(info.splat!==undefined?`${info.splat}`:" "))
  ),
  transports: [
    new (winston.transports.Console)({ level: loggerLevel }),
  ]
});
module.exports = logger;