In order to match a timestamp to an offset, Moment Timezone uses a Zone
object.
Though you shouldn't even need to use it, this object's constructor is available
on the moment.tz.Zone
namespace.
This object has 5 properties.
{
name : 'America/Los_Angeles', // the unique identifier
abbrs : ['PDT', 'PST'], // the abbreviations
untils : [1414918800000, 1425808800000], // the timestamps in milliseconds
offsets : [420, 480], // the offsets in minutes
population : 15000000 // a rough population count for the largest city in this zone
}