diff --git a/.travis.yml b/.travis.yml
index ee44bf1..1f987d1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,8 +2,6 @@ language: node_js
 
 node_js:
   - stable
-  - v0.10
-  - v0.12
   - v4
   - v5
   - v6
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 251cb13..4f295ab 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+## 4.0.0
+
+- Drop support for Node.js `< 4.0.0`
+- Remove dependency on `lodash`
+
 ## 3.2.0
 
 - Add `mon` unit ([@IanMitchell](https://github.com/IanMitchell))
diff --git a/README.md b/README.md
index 2843ac2..fc9796e 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Timestring
+# timestring
 
 [![Version](https://img.shields.io/npm/v/timestring.svg?style=flat-square)](https://www.npmjs.com/package/timestring)
 [![Build Status](https://img.shields.io/travis/mike182uk/timestring.svg?style=flat-square)](http://travis-ci.org/mike182uk/timestring)
@@ -20,10 +20,10 @@ npm install --save timestring
 ### Overview
 
 ```js
-var timestring = require('timestring')
+const timestring = require('timestring')
 
-var str = '1h 15m'
-var time = timestring(str)
+let str = '1h 15m'
+let time = timestring(str)
 
 console.log(time) // will log 4500
 ```
@@ -33,8 +33,10 @@ console.log(time) // will log 4500
 The time string can contain as many time groups as needed:
 
 ```js
-var str = '1d 3h 25m 18s'
-var time = timestring(str)
+const timestring = require('timestring')
+
+let str = '1d 3h 25m 18s'
+let time = timestring(str)
 
 console.log(time) // will log 98718
 ```
@@ -42,15 +44,17 @@ console.log(time) // will log 98718
 and can be as messy as you like:
 
 ```js
-var str = '1 d    3HOurS 25              min         1   8s'
-var time = timestring(str)
+const timestring = require('timestring')
+
+let str = '1 d    3HOurS 25              min         1   8s'
+let time = timestring(str)
 
 console.log(time) // will log 98718
 ```
 
 ### Keywords
 
-Timestring will parse the following keywords into time values:
+`timestring` will parse the following keywords into time values:
 
 1. `ms, milli, millisecond, milliseconds` - will parse to milliseconds
 2. `s, sec, secs, second, seconds` - will parse to seconds
@@ -64,8 +68,10 @@ Timestring will parse the following keywords into time values:
 Keywords can be used interchangeably:
 
 ```js
-var str = '1day 15h 20minutes 15s'
-var time = timestring(str)
+const timestring = require('timestring')
+
+let str = '1day 15h 20minutes 15s'
+let time = timestring(str)
 
 console.log(time) // will log 141615
 ```
@@ -84,11 +90,17 @@ By default the return time value will be in seconds. This can be changed by pass
 8. `y` - Years
 
 ```js
-var str = '22h 16m'
+const timestring = require('timestring')
+
+let str = '22h 16m'
 
-var hours = timestring(str, 'h') // 22.266666666666666
-var days = timestring(str, 'd') // 0.9277777777777778
-var weeks = timestring(str, 'w') // 0.13253968253968254
+let hours = timestring(str, 'h')
+let days = timestring(str, 'd')
+let weeks = timestring(str, 'w')
+
+console.log(hours) // will log 22.266666666666666
+console.log(days) // will log 0.9277777777777778
+console.log(weeks) // will log 0.13253968253968254
 ```
 
 ### Optional Configuration
@@ -110,12 +122,14 @@ The following options are configurable:
 4. `monthsPerYear`
 
 ```js
-var str = '1d'
-var opts = {
-	hoursPerDay: 1
+const timestring = require('timestring')
+
+let str = '1d'
+let opts = {
+  hoursPerDay: 1
 }
 
-var time = timestring(str, 'h', opts)
+let time = timestring(str, 'h', opts)
 
 console.log(time) // will log 1
 ```
@@ -127,13 +141,15 @@ This would be useful for specific application needs.
 *Example  - Employees of my company work 7.5 hours a day, and only work 5 days a week. In my time tracking app, when they type `1d` i want 7.5 hours to be tracked. When they type `1w` i want 5 days to be tracked etc.*
 
 ```js
-var opts = {
-	hoursPerDay: 7.5,
-	daysPerWeek: 5
+const timestring = require('timestring')
+
+let opts = {
+  hoursPerDay: 7.5,
+  daysPerWeek: 5
 }
 
-var hoursToday = timestring('1d', 'h', opts)
-var daysThisWeek = timestring('1w', 'd', opts)
+let hoursToday = timestring('1d', 'h', opts)
+let daysThisWeek = timestring('1w', 'd', opts)
 
 console.log(hoursToday) // will log 7.5
 console.log(daysThisWeek) // will log 5
diff --git a/index.js b/index.js
index a148aa8..f3ff176 100644
--- a/index.js
+++ b/index.js
@@ -1,4 +1,4 @@
-var _ = require('lodash')
+'use strict'
 
 /**
  * Exports
@@ -12,7 +12,7 @@ module.exports = parseTimestring
  * @type {Object}
  */
 
-var defaultOpts = {
+const DEFAULT_OPTS = {
   hoursPerDay: 24,
   daysPerWeek: 7,
   weeksPerMonth: 4,
@@ -25,7 +25,7 @@ var defaultOpts = {
  * @type {Object}
  */
 
-var unitMap = {
+const UNIT_MAP = {
   ms: ['ms', 'milli', 'millisecond', 'milliseconds'],
   s: ['s', 'sec', 'secs', 'second', 'seconds'],
   m: ['m', 'min', 'mins', 'minute', 'minutes'],
@@ -39,26 +39,26 @@ var unitMap = {
 /**
  * Parse a timestring
  *
- * @param {string} string
- * @param {string} [returnUnit]
- * @param {Object} [opts]
- * @return {number}
+ * @param  {String} string
+ * @param  {String} returnUnit
+ * @param  {Object} opts
+ * @return {Number}
  */
 
 function parseTimestring (string, returnUnit, opts) {
-  opts = _.extend(_.clone(defaultOpts), opts || {})
+  opts = Object.assign({}, DEFAULT_OPTS, opts || {})
 
-  var totalSeconds = 0
-  var unitValues = getUnitValues(opts)
-  var groups = string
+  let totalSeconds = 0
+  let unitValues = getUnitValues(opts)
+  let groups = string
     .toLowerCase()
     .replace(/[^.\w+-]+/g, '')
     .match(/[-+]?[0-9]+[a-z]+/g)
 
   if (groups !== null) {
-    _.each(groups, function (group) {
-      var value = group.match(/[0-9]+/g)[0]
-      var unit = group.match(/[a-z]+/g)[0]
+    groups.forEach(group => {
+      let value = group.match(/[0-9]+/g)[0]
+      let unit = group.match(/[a-z]+/g)[0]
 
       totalSeconds += getSeconds(value, unit, unitValues)
     })
@@ -74,12 +74,12 @@ function parseTimestring (string, returnUnit, opts) {
 /**
  * Get unit values based on the passed options
  *
- * @param {Object} opts
+ * @param   {Object} opts
  * @returns {Object}
  */
 
 function getUnitValues (opts) {
-  var unitValues = {
+  let unitValues = {
     ms: 0.001,
     s: 1,
     m: 60,
@@ -97,48 +97,42 @@ function getUnitValues (opts) {
 /**
  * Get the key for a unit
  *
- * @param {string} unit
- * @returns {string}
+ * @param   {String} unit
+ * @returns {String}
  */
 
 function getUnitKey (unit) {
-  for (var k in unitMap) {
-    for (var u in unitMap[k]) {
-      if (unit === unitMap[k][u]) {
-        return k
-      }
+  for (let key of Object.keys(UNIT_MAP)) {
+    if (UNIT_MAP[key].indexOf(unit) > -1) {
+      return key
     }
   }
 
-  throw new Error('The unit [' + unit + '] is not supported by timestring')
+  throw new Error(`The unit [${unit}] is not supported by timestring`)
 }
 
 /**
  *  Get the number of seconds for a value, based on the unit
  *
- * @param {number} value
- * @param {string} unit
- * @param {Object} unitValues
- * @returns {number}
+ * @param   {Number} value
+ * @param   {String} unit
+ * @param   {Object} unitValues
+ * @returns {Number}
  */
 
 function getSeconds (value, unit, unitValues) {
-  var baseValue = unitValues[getUnitKey(unit)]
-
-  return value * baseValue
+  return value * unitValues[getUnitKey(unit)]
 }
 
 /**
  * Convert a value from its existing unit to a new unit
  *
- * @param {number} value
- * @param {string} unit
- * @param {Object} unitValues
- * @returns {number}
+ * @param   {Number} value
+ * @param   {String} unit
+ * @param   {Object} unitValues
+ * @returns {Number}
  */
 
 function convert (value, unit, unitValues) {
-  var baseValue = unitValues[getUnitKey(unit)]
-
-  return value / baseValue
+  return value / unitValues[getUnitKey(unit)]
 }
diff --git a/package.json b/package.json
index 586bb6b..68e3276 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "timestring",
-  "version": "3.2.0",
+  "version": "4.0.0",
   "description": "Parse a human readable time string into a time based value",
   "main": "index.js",
   "scripts": {
@@ -23,15 +23,10 @@
     "time",
     "timestring",
     "duration",
-    "parse",
-    "string",
     "date"
   ],
   "engines": {
-    "node": ">=0.10"
-  },
-  "dependencies": {
-    "lodash": "^4.0.0"
+    "node": ">=4"
   },
   "devDependencies": {
     "chai": "^3.4.1",
diff --git a/test.js b/test.js
index 0e66d1c..5d2d1e7 100644
--- a/test.js
+++ b/test.js
@@ -1,12 +1,14 @@
+'use strict'
+
 /* globals describe, it */
 
-var chai = require('chai')
-var expect = chai.expect
+const chai = require('chai')
+const timestring = require('./index')
 
-var timestring = require('./index')
+const expect = chai.expect
 
-describe('timestring', function () {
-  it('can parse a timestring', function () {
+describe('timestring', () => {
+  it('can parse a timestring', () => {
     expect(timestring('500ms')).to.equal(0.5)
     expect(timestring('1s')).to.equal(1)
     expect(timestring('1m')).to.equal(60)
@@ -17,8 +19,8 @@ describe('timestring', function () {
     expect(timestring('1y')).to.equal(29030400)
   })
 
-  it('can parse different unit identifiers', function () {
-    var unitMap = {
+  it('can parse different unit identifiers', () => {
+    let unitMap = {
       ms: ['ms', 'milli', 'millisecond', 'milliseconds'],
       s: ['s', 'sec', 'secs', 'second', 'seconds'],
       m: ['m', 'min', 'mins', 'minute', 'minutes'],
@@ -29,47 +31,47 @@ describe('timestring', function () {
       y: ['y', 'yr', 'yrs', 'year', 'years']
     }
 
-    unitMap.ms.forEach(function (msUnit) {
-      expect(timestring('500 ' + msUnit)).to.equal(0.5)
+    unitMap.ms.forEach(unit => {
+      expect(timestring(`500 ${unit}`)).to.equal(0.5)
     })
 
-    unitMap.s.forEach(function (sUnit) {
-      expect(timestring('3 ' + sUnit)).to.equal(3)
+    unitMap.s.forEach(unit => {
+      expect(timestring(`3 ${unit}`)).to.equal(3)
     })
 
-    unitMap.m.forEach(function (mUnit) {
-      expect(timestring('2 ' + mUnit)).to.equal(120)
+    unitMap.m.forEach(unit => {
+      expect(timestring(`2 ${unit}`)).to.equal(120)
     })
 
-    unitMap.h.forEach(function (hUnit) {
-      expect(timestring('7 ' + hUnit)).to.equal(25200)
+    unitMap.h.forEach(unit => {
+      expect(timestring(`7 ${unit}`)).to.equal(25200)
     })
 
-    unitMap.d.forEach(function (dUnit) {
-      expect(timestring('4 ' + dUnit)).to.equal(345600)
+    unitMap.d.forEach(unit => {
+      expect(timestring(`4 ${unit}`)).to.equal(345600)
     })
 
-    unitMap.w.forEach(function (wUnit) {
-      expect(timestring('2 ' + wUnit)).to.equal(1209600)
+    unitMap.w.forEach(unit => {
+      expect(timestring(`2 ${unit}`)).to.equal(1209600)
     })
 
-    unitMap.mth.forEach(function (mthUnit) {
-      expect(timestring('9 ' + mthUnit)).to.equal(21772800)
+    unitMap.mth.forEach(unit => {
+      expect(timestring(`9 ${unit}`)).to.equal(21772800)
     })
 
-    unitMap.y.forEach(function (yUnit) {
-      expect(timestring('1 ' + yUnit)).to.equal(29030400)
+    unitMap.y.forEach(unit => {
+      expect(timestring(`1 ${unit}`)).to.equal(29030400)
     })
   })
 
-  it('can return a value in a specified unit', function () {
+  it('can return a value in a specified unit', () => {
     expect(timestring('1m', 'ms')).to.equal(60000)
     expect(timestring('5m', 's')).to.equal(300)
     expect(timestring('5m', 'm')).to.equal(5)
   })
 
-  it('uses the passed options instead of the defaults', function () {
-    var opts = {
+  it('uses the passed options instead of the defaults', () => {
+    let opts = {
       hoursPerDay: 1,
       daysPerWeek: 2,
       weeksPerMonth: 3,
@@ -82,11 +84,11 @@ describe('timestring', function () {
     expect(timestring('1y', 'mth', opts)).to.equal(4)
   })
 
-  it('throws an error when an invalid unit is used in the timestring', function () {
-    expect(function () { timestring('1g') }).to.throw(Error)
+  it('throws an error when an invalid unit is used in the timestring', () => {
+    expect(() => timestring('1g')).to.throw(Error)
   })
 
-  it('can parse a messy time string', function () {
+  it('can parse a messy time string', () => {
     expect(timestring('5   D a YS    4 h   2 0     mI  nS')).to.equal(447600)
   })
 })
diff --git a/yarn.lock b/yarn.lock
index 538d67f..b3da14b 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -609,6 +609,10 @@ esprima@2.7.x, esprima@^2.6.0, esprima@^2.7.1:
   version "2.7.3"
   resolved "https://registry.yarnpkg.com/esprima/-/esprima-2.7.3.tgz#96e3b70d5779f6ad49cd032673d1c312767ba581"
 
+esprima@^3.1.1:
+  version "3.1.3"
+  resolved "https://registry.yarnpkg.com/esprima/-/esprima-3.1.3.tgz#fdca51cee6133895e3c88d535ce49dbff62a4633"
+
 esquery@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/esquery/-/esquery-1.0.0.tgz#cfba8b57d7fba93f17298a8a006a04cda13d80fa"
@@ -1020,13 +1024,20 @@ js-tokens@^3.0.0:
   version "3.0.1"
   resolved "https://registry.yarnpkg.com/js-tokens/-/js-tokens-3.0.1.tgz#08e9f132484a2c45a30907e9dc4d5567b7f114d7"
 
-js-yaml@3.6.1, js-yaml@3.x, js-yaml@^3.5.1:
+js-yaml@3.6.1:
   version "3.6.1"
   resolved "https://registry.yarnpkg.com/js-yaml/-/js-yaml-3.6.1.tgz#6e5fe67d8b205ce4d22fad05b7781e8dadcc4b30"
   dependencies:
     argparse "^1.0.7"
     esprima "^2.6.0"
 
+js-yaml@3.x, js-yaml@^3.5.1:
+  version "3.8.3"
+  resolved "https://registry.yarnpkg.com/js-yaml/-/js-yaml-3.8.3.tgz#33a05ec481c850c8875929166fe1beb61c728766"
+  dependencies:
+    argparse "^1.0.7"
+    esprima "^3.1.1"
+
 jsbn@~0.1.0:
   version "0.1.1"
   resolved "https://registry.yarnpkg.com/jsbn/-/jsbn-0.1.1.tgz#a5e654c2e5a2deb5f201d96cefbca80c0ef2f513"
@@ -1668,7 +1679,7 @@ strip-json-comments@~2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/strip-json-comments/-/strip-json-comments-2.0.1.tgz#3c531942e908c2697c0ec344858c286c7ca0a60a"
 
-supports-color@3.1.2, supports-color@^3.1.0:
+supports-color@3.1.2:
   version "3.1.2"
   resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-3.1.2.tgz#72a262894d9d408b956ca05ff37b2ed8a6e2a2d5"
   dependencies:
@@ -1678,6 +1689,12 @@ supports-color@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-2.0.0.tgz#535d045ce6b6363fa40117084629995e9df324c7"
 
+supports-color@^3.1.0:
+  version "3.2.3"
+  resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-3.2.3.tgz#65ac0504b3954171d8a64946b2ae3cbb8a5f54f6"
+  dependencies:
+    has-flag "^1.0.0"
+
 table@^3.7.8:
   version "3.8.3"
   resolved "https://registry.yarnpkg.com/table/-/table-3.8.3.tgz#2bbc542f0fda9861a755d3947fefd8b3f513855f"