Alright, here's a really niche find from my digging around: how to change Passport Registration Date (and subsequently also achievement dates for Nook Miles but I won't go into that here), for anyone who wants it. I was trying to find changing island fruit, but I fell asleep before I finished digging around.
Much like in New Leaf, the Registration Date is formatted inside the hex data as
YY YY MM DD
However, it should be noted that the Year value will be transposed inside the hex. What do I mean by this? I'll walk you through an example. Let's say your Registration Date is March 19, 2020. Inside the hex, that would be:
E4 07 03 13
YY YY MM DD
So, how do I get these numbers?:
Month of March = 03 (values listed below)
19th Day = 13 (values listed below)
2020 = 07 E4 (a decimal to hex converter will give you this value)
March 19 2020 therefore:
03 13 07 E4
MM DD YY YY
But wait, I said E4 07 just a second ago. Indeed. For the year values, specifically, you'll need to flip the digits after you calculate them via hex. Which means that 03 13 07 E4 becomes 03 13 E4 07 for March 19, 2020.
Leaving us with 03, 13, E4 07, or MM, DD, YY YY, and New Leaf requires a specific format: you'll just need to move the YY YY digits to the front so that your format is properly YY YY MM DD, or:
E4 07 03 13
YY YY MM DD
Registration Date Offset is 001D71F8 - 001D71FB
Code:
MONTH VALUES
00 Blank
01 January
02 February
03 March
04 April
05 May
06 June
07 July
08 August
09 September
0A October
0B November
0C December
Code:
DAY VALUES
00 Blank
01 1
02 2
03 3
04 4
05 5
06 6
07 7
08 8
09 9
0A 10
0B 11
0C 12
0D 13
0E 14
0F 15
10 16
11 17
12 18
13 19
14 20
15 21
16 22
17 23
18 24
19 25
1A 26
1B 27
1C 28
1D 29
1E 30
1F 31