Hello!
I’m from a place where my brain is hard-wired to see the first day of the week as Monday, as Saturday and Sunday are the weekend, and so I can’t for the life of me get used to Sunday being the first day in a calendar.
I like the Heat Map widget, so I’d like to customize it to show the “correct” day as the first day of the week!
Haha, yeah, that was also the thing that was the hardest to get used to after I switched my smartphone and google account to Japanese. I still don’t get why Japanese start the week on Sundays 
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Good luck with getting your request granted.
Never thought about this before. For me the week starts on a Sunday. And naturally ends on a Saturday. I dont think there’s any difference since its the same week no matter how you slice it.
I could find a reason for Sunday calendars, but the reason for Monday starts isn’t as clear. Even the research papers are too murky and it devolves into asking why humans are the way they are. Just are.
Workweek starts on Monday?
ISO 8601?
The weekend shouldn’t also be the start of a week?
It just is?
Well, I’m the opposite, I can very easily find a way for Monday calendars, but the reason for having the week start at Sunday makes no sense to me. 
It is based on the workweek, indeed. That’s why we call Saturday and Sunday the weekend days, because they’re the days you get to yourself after you’re done with a normal daytime job. Even places that start their calendar at Sunday call Sunday a weekend day.
So like, Sunday is part of the END of the week, everyone everywhere agrees that Sunday is a weekend day. It makes no sense to me to then consider it the start of the new week, when it’s also the end of the old week. You’re never gonna experience a time that’s both Monday and Tuesday, as it can only be Tuesday because Monday has ended. Similarly, you will never experience being in both February and January at the same time. It can only be February because January has ended, it can only be 2026 because 2025 has ended. Because that’s how time works, it can only be a new time because the old time is in the past.
Weeks are the same way, a new one can only start because the previous one has ended. So Sunday can’t be both the new week and the old week, it has to pick one. Either it is the end of a week, or the start of a week, it can’t be part of two weeks any more than any period of time can be part of two days, two months or two years. I genuinely don’t understand how you find these reasons unclear and murky, how is it not completely logical and sensible to say a day can’t be part of two weeks at the same time? That it can’t be both the end and start of a week? 
But as you say, this is mostly just about what you’re used to. You internalize whatever system you’re used to, and make it feel like that’s just how it’s supposed to be. Which is why it’s very difficult for me to adapt to the calendar view that to me is kind of nonsensical. It’s easy for you to say it’s the same week no matter how you slice it, because you get the calendar the way you’re used to it. To me, it really isn’t the same at all 
I found this thread because I agree with you and also want to be able to set Monday as first day of week for heat map. But thinking about it again you could argue that this is part of WaniKani’s holistic learning experience, so you immerse more into Japanese customs and culture.
Anyway wouldn’t be mad if this feature is added in the future!
Tied to religion. In countries where religions with Sunday being the Holy day are/were predominant you will find that they tend to have structured their calendars making Sunday the start of the week.
This was the case in most of Europe as well, but that changed with most countries there adopting and following the ISO standard which was published in the 80s sometime. Some of us older folks here will have been around and may remember that. Many countries did not follow suite, especially in the Americans where the feeling was that religious tradition trumped “arbitrary” standards dictated by scientist type folks.
Ironically, or perhaps more aptly interestingly, the reason that Japan has a calendar with Sunday as the first day is that they adopted a calendar with Sunday as the first day of the week when they adopted the calendar system from China. And then during the Meiji restoration adopted the “Western calendar” in order to align with international standards (at the time). Which of course, is not aligned with international standards post ISO-8601 in the 1980s, but like Canada and America, they did not want to make that change. Maybe someone said “Wait, this is getting ridiculous. How many times do we need to keep changing our calendar. No more I say. No more!!” 
But in Japanese of course….
I want to speak to the manager of whoever made the calendar and decided the year should end on a Wednesday. Excuse me? The year should always end on a Friday.
It has been done. It exists. You will just need to start a movement to get folks to adopt it.
Easier said than done, apparently the calendar itself is out of order as well. October meaning 8th month happens in the 10th month because of roman emperors Julius and Augustus?
never heard of bookends? 
do you put them both on one side? 
It doesn’t even stop there! Sept is 7, oct 8, nov 9 and dec 10. Our calendar truly does suck
I wish we’d get together and make a new ISO standard for calendars from scratch, like we did with so many other types of measurements. There’s a lot of good proposals out there!
Although it’ll never be perfect since the earth didn’t have the courtesy to keep a consistent 1:1 ratio between the speed it turns around its own axis and the time it takes it to complete a full orbit of the sun, or even stick to a nice round number of days in a year to be easily divisible 
I don’t think this is as good of a comeback as you think it is
hey bud, you’re the one thinking if someone says sunday is the start of the week, they think it’s somehow both the first and last day of the week?? 
i’m just saying an “end” can be the start, without being also last
Be a nice feature. Though I always looked at Weekend more look bookend. The day at the two ends of the week, looking at a week like a line.
But that’s my weird brain.