currentTimezone.js

// Some basic javascript Date examples

// NOTE: Javascript dates have 0 indexed months, because they are awesome

// January 1, 2012 (Chicago, IL)
var firstOfYear = new Date(2012, 0, 1),
    // 6 Hour offset (before DST change)
    hoursOffset = firstOfYear.getTimezoneOffset() / 60; 

// April 1, 2012 (Chicago, IL)
var afterDST = new Date(2012, 3, 1),
    // 5 Hour offset (after DST change)
    hoursOffset = afterDST.getTimezoneOffset() / 60;

// November 16, 2012 (Chicago, IL)
var postDate = new Date(2012, 10, 16),
    // 6 Hour offset (after DST change back)
    hoursOffset = postDate.getTimezoneOffset() / 60;

olson.txt

# US central time, represented by Chicago

# Alabama, Arkansas, Florida panhandle (Bay, Calhoun, Escambia,
# Gulf, Holmes, Jackson, Okaloosa, Santa Rosa, Walton, and
# Washington counties), Illinois, western Indiana
# (Gibson, Jasper, Lake, LaPorte, Newton, Porter, Posey, Spencer,
# Vanderburgh, and Warrick counties), Iowa, most of Kansas, western
# Kentucky, Louisiana, Minnesota, Mississippi, Missouri, eastern
# Nebraska, eastern North Dakota, Oklahoma, eastern South Dakota,
# western Tennessee, most of Texas, Wisconsin

# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER
Rule	Chicago	1920	only	-	Jun	13	2:00	1:00	D
Rule	Chicago	1920	1921	-	Oct	lastSun	2:00	0	S
Rule	Chicago	1921	only	-	Mar	lastSun	2:00	1:00	D
Rule	Chicago	1922	1966	-	Apr	lastSun	2:00	1:00	D
Rule	Chicago	1922	1954	-	Sep	lastSun	2:00	0	S
Rule	Chicago	1955	1966	-	Oct	lastSun	2:00	0	S

otherTimezoneExample.js

var someUTCDate = new Date(new Date().getTime()),
    chicagoWallTime = WallTime.UTCToWallTime(someUTCDate, "America/Chicago"),
    backToUTCTIme = WallTime.WallTimeToUTC("America/Chicago", chicagoWallTime);

walltimeexample.html

<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>