I'd like to change my time zone.
I signed up while I was abroad in Germany. I'm now in the US, on Pacific time, and I'm about to move to the Eastern Time Zone. Can I change my time zone to Eastern, so that if I earn XP after 4pm I receive them for the day that I'm going to actually be in?
Also, there's a curious problem; even though the streak counter resets on German time, the app uses the time on my phone to determine the current day. So I have less than 24 hours every day where the two line up.
For example: From midnight-4pm, I can earn XP for the day that I'm in. After 4pm, I only earn points for the next day, but the app still tells me that I need more points to hit my goal for the current day. But at that point, it's impossible! It puts me into a more limited time box if I want to keep my streak going.
I tend to work late on some nights. So, I went to study at 1AM and found I'd lost my streak, even though it was the same day for me. Conversely, I studied at 1AM and want to do it again at 10:30 PM, but it counts as the same day. I'd really like to see a way to break up days at slightly more unusual timepoints.
So would you wait until 4AM to celebrate the New Year? Of course not, the whole world celebrates it at Midnight in their local time zone.
There would be chaos if we all chose an arbitrary time for when a day begins. That is why it is standardised by International agreement.
You're right in that we shouldn't change the official end of the date for technical purposes (there would be chaos). But in this case, think of it more like a person working a night-shift at a store. You'd say they were working one shift a day, from 8PM-4AM, rather than two shifts a day, from 12AM-4AM and 8PM-11:59:59AM. Additionally, if you tried to do Duolingo on you lunch break (somewhere just before 12AM, sometimes just after), you'd find it impossible to maintain a streak on the site, even if you studied every day.