Timezone conversion to same timezone keeping time returns wrong valueOf

[fabio-moyano-s1]

Describe the bug
When you convert a date to the same timezone and with the keepLocalTime set as true the valueOf function returns the wrong milis value.

See this code snippet:

import dayjs from 'dayjs';
import timezone from 'dayjs/plugin/timezone';
import utc from 'dayjs/plugin/utc';

dayjs.extend(timezone);
dayjs.extend(utc);

// Update: Apparently it only happens when the timezone is UTC
const timezoneToUse = 'UTC'

// Set default timezone
dayjs.tz.setDefault(timezoneToUse);

const date1 = dayjs.tz('2021-08-09T12:45:00Z');
console.log(date1.format()); // 2021-08-09T12:45:00Z
console.log(date1.valueOf()); // 1628513100000

const date2 = dayjs.tz('2021-08-09T12:45:00Z').tz(timezoneToUse);
console.log(date2.format()); //  2021-08-09T12:45:00Z
console.log(date2.valueOf()); // 1628513100000

const date3 = dayjs.tz('2021-08-09T12:45:00Z').tz(timezoneToUse, true);
console.log(date3.format()); // 2021-08-09T12:45:00Z
console.log(date3.valueOf()); // 1628520300000 -> why?

Expected behavior
valueOf should return the same value regardless if you set keepLocalTime on or off if you are parsing from the same timezone.

Information

• Day.js Version v1.11.13
• OS: MacOS Sonoma 14.7
• Browser Chrome v129.0.6668.91
• Time zone: Europe/Prague