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
}