build says it failed at imported module, but app is still built and works.

Complete noob in react, this is day 2 of my learning. but basically:

1. i added tiny-relative-date to the app.
2. i import like import relativeDate from 'tiny-relative-date';
3. i run npm run build and then it says it failed, but the app still works in the browser.

output:

Garrett Morris@DESKTOP-U5VCBFV MINGW64 /e/blog
$ npm run build

> blog@0.1.0 build E:\blog
> react-scripts build

Creating an optimized production build...
Failed to compile.

Failed to minify the code from this file:

        ./node_modules/tiny-relative-date/src/factory.js:1

Read more here: http://bit.ly/2tRViJ9


npm ERR! Windows_NT 10.0.16299
npm ERR! argv "C:\\Program Files\\nodejs\\node.exe" "C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npm-cli.js" "run" "build"
npm ERR! node v6.9.1
npm ERR! npm  v3.10.8
npm ERR! code ELIFECYCLE
npm ERR! blog@0.1.0 build: `react-scripts build`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the blog@0.1.0 build script 'react-scripts build'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the blog package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     react-scripts build
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs blog
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls blog
npm ERR! There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     E:\blog\npm-debug.log

[Timer]

And herein lies the problem; this is the ES6 feature the bit.ly link mentions is not supported:

const calculateDelta = (now, date) => Math.round(Math.abs(now - date) / 1000)

[Timer]

start and build are separate; try a different library! https://date-fns.org/v1.29.0/docs/distanceInWordsToNow

(and read the link provided in the error for reasoning)