moment().zone(1) returns UTC-1:00

[moment]

moment().zone(1) returns UTC-1:00

[timrwood]

This is unfortunately a feature.

When moment#zone was first added in version 1.2.0, it was just a wrapper for Date.prototype.getTimezoneOffset, which actually has some weirdness to it.

The time-zone offset is the difference, in minutes, between UTC and local time. Note that this means that the offset is positive if the local timezone is behind UTC and negative if it is ahead. For example, if your time zone is UTC+10 (Australian Eastern Standard Time), -600 will be returned.

via https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/getTimezoneOffset

Then, in version 2.1.0, the ability to set the offset using moment#zone was added. https://gist.github.com/timrwood/b8c2d90d528eddb53ab5#added-ability-to-set-offset-with-momentzone

In order to keep compatibility with the output of moment#zone, a numeric input to moment#zone actually needs to be the negative of the string input.

moment().zone(240).format();      // 2014-06-24T12:41:16-04:00
moment().zone('-04:00').format(); // 2014-06-24T12:41:16-04:00

In hindsight, it would have been better to invert the output from Date.prototype.getTimezoneOffset, but I didn't realize it was backwards until it was far too late.