Timezone plugin unexpected daylight calculation

**Describe the bug**
When using the timezone plugin the date calculated by `dayjs` is unexpected for `daylight datetime` calculation, I'm comparing towards moment-timezone.

**Expected behaviour**
```
const moment = require('moment-timezone');
const dayjs = require('dayjs');
const utc = require('dayjs/plugin/utc');
const tz = require('dayjs/plugin/timezone');

dayjs.extend(utc);
dayjs.extend(tz);

const timezone = 'America/Vancouver';
const currentDate = new Date('2020-03-08T12:00-07:00');
const nowMoment = moment(currentDate);
const nowDayJs = dayjs(currentDate);

// milliseconds for currentDate: 1583694000000
console.log(nowDayJs.valueOf() === nowMoment.valueOf()); // -> true

// daylight
// https://www.timetemperature.com/canada/daylight_saving_time_canada.shtml
const plainDate = currentDate.toISOString().slice(0, 10); // 2020-08-08
const dlMoment = moment.tz(plainDate, timezone).set({
hour: 12,
minute: 30
});
const dlDayJs = dayjs.tz(plainDate, timezone)
.set('hour', 12)
.set('minute', 30);
console.log(dlDayJs.format() === dlMoment.format()); // -> false (true expected)
// 2020-03-07T12:30:00-08:00 !== 2020-03-08T12:30:00-07:00

```

**Information**
- dayjs: 1.8.33
- moment-timezone: 0.5.31
- OS: Ubuntu 18.04.4 LTS
- Nodejs 12.18.0
- Time zone: GMT-07:00 DST (Pacific Daylight Time)

Start by reproducing the supplied Node.js example with the timezone and UTC plugins, then inspect the timezone plugin entry point and related tests. Compare the daylight-saving result with moment-timezone for the stated date and timezone; done means the Day.js formatted value matches the expected 2020-03-08T12:30:00-07:00 result.

Written by the indexing model from the issue text.