Timewarp and Timezones

[clintropolis]

Queries using both timewarp post processing and a PeriodGranularity specifying a timezone do not correctly offset dates if a daylight savings time transition occurs between the source data interval and the query interval. For example, a query of the form

{
      "queryType": "timeseries",
      "dataSource": "some_datasource",
      "intervals": "2017-12-04T08Z/2017-12-011T08Z",
      "granularity": {
        "type": "period",
        "period": "P1D",
        "timeZone": "America/Los_Angeles"
      },
      "context": {
        "postProcessing": {
          "type": "timewarp",
          "dataInterval": "2015-06-22/2015-07-20",
          "period": "P1D",
          "origin": "2015-07-20"
        },
        ...

returns results that are shifted by an hour

[ {
  "timestamp" : "2017-12-03T23:00:00.000-08:00",
  "result" : ...
}, {
  "timestamp" : "2017-12-04T23:00:00.000-08:00",
  "result" : ...
}
...

Currently, TimewarpOperator is unaware of the timezone and thus any daylight savings time shifts that might occur and should be taken into account when calculating the offset.