3DS: In-game RTC desyncs from system time

[CaptainSwag101]

This may technically be 2 issues, but I think they may both have a common cause. I am using the v0.6.0 release of mGBA, playing on a New 3DS XL with Luma3DS v8.1, and I have encountered this issue on both the CIA and 3DSX builds of mGBA. I have not encountered this problem with the PC versions of mGBA, but I have not done as much testing on those systems. I do not believe this is a regression introduced in v0.6.0, as I recall having this issue in version 0.5.2 as well.

First, I was playing Pokemon Prism, and at the start of the game I did my best to set the in-game clock to the same date/ time as my 3DS. However, after playing the game for a while, I saved the game (and also did a savestate) and closed mGBA, and when I reopened it and started playing the game again, I noticed that the in-game clock was behind my system time by roughly the amount of time I had stopped playing. However, I believe this is incorrect behavior, as the in-game clock should be kept in sync with the system time.

Furthermore, whenever I put the 3DS into sleep mode with the game open, the in-game time speeds up by a considerable amount. I started playing the game on Saturday July 22, and after leaving the system asleep for a day or two, my in-game clock said that the date was somewhere in the middle of October! And when I opened the game today, it now says it's December. Even if mGBA isn't supposed to manually change the RTC to the system time, I believe that the RTC still shouldn't run so fast when the system is in sleep mode.

[endrift]

Can you confirm that this happens for GBA games too, e.g. Ruby? The GB RTC is kind of buggy and I haven't figured out why, despite having written tests.

[CaptainSwag101]

Nope, Pokemon Emerald works fine, and stays in sync with the system time while the emulator is closed or the system is asleep.

[endrift]

I have a tentative fix for this, but it requires more time (quite literally) to test before it's ready.

[endrift]

Note that this test is not hugely well tested yet, so I'd appreciate more testing. I can reopen the bug if it's not working still.

[CaptainSwag101]

Awesome, I'll be sure to test tomorrow and let you know! Thanks again for all the hard work!

[endrift]

Confirmed that letting it sleep overnight leads to the expected result. Will try leaving the emulator not running for a few hours next.