Walltime-js is a JavaScript library for easily translating a UTC time to a "Wall Time" for a particular time zone.

Dates in JavaScript do not properly account for daylight savings time for regions other than your own browser configured time zone.

For example:

• Your API sends UTC times in JSON but you need to display them for Chicago time zone to a user viewing your page in Los Angeles.
• What was the UTC Time on May 24, 1844 at 9:00 AM in Baltimore, Maryland?

<script src="/path/to/walltime-data.js"></script>
<script src="/path/to/walltime.js"></script>
<script type="text/javascript">
    var someUTCDate = new Date(new Date().getTime()),
        chicagoWallTime = WallTime.UTCToWallTime(someUTCDate, "America/Chicago");
</script>

To limit the size of WallTime.js, you should only use the data for the time zone files you need.

By default, walltime-data.js contains northamerica, europe and australasia, which encompass most of the world, but is 479k (minified). By narrowing it down to just northamerica, you could save 300k. Adding gzip compression could get you down as low as 16k.

This project uses Node.js and CoffeeScript; go and install them if you don't have them.

To get the latest Olson files

git submodule init && git submodule update

To build all the data for all the time zone files

cake data

To build data for northamerica only

cake -f northamerica data

To build data for northamerica and europe

cake -f northamerica -f europe data

To build data for America/Chicago only

cake -f northamerica -z America/Chicago data

To build individual data files for each time zone

cake individual

By default the files are saved to ./client/walltime.js etc.

To get setup

# Clone the repo
git clone https://github.com/sproutsocial/walltime-js.git
# Install the dependencies
npm install

To run tests

cake test

To make new tests, create a new spec coffee file in the test directory.