What vendors set up permanent shop

I have seen the future and the past. I have time traveled for hundreds of years (by adjusting my Switch system clock) and this is what I learned:

• There is no major effect. No nagging, no obvious penalties, despite what IGN said. Indeed, on the plus side, progressing into the future earns interest on your Nook Bank balance (in the ATM/ADM), maxing out at 99k bells at a time.
• No residents left town, in my case. Caveat emptor: I did this before actively recruiting new townspeople. For what it's worth, I ignored townspeople when I time traveled (man on a mission), which might have stopped the game from registering that I had "ignored" the residents. For example, if I progress into the future and talked to a resident, they'll remember that it's been weeks/months/longer since we last spoke, but once I returned into the past and talked with the residents, they wouldn't say anything about the time passed.
• I also didn't especially notice more weeds or anything falling into disarray, but that might have been because I traveled between winters, when snow covered the ground.
• Not specific to time travel but to putting down the game in general, if you haven't been "in-game" in a while, there may be changes that are not recapped in Isabelle's morning announcement, such as new residents who came and were ostensibly announced while you were gone.

There are three common symbols on your DIY cards:

• Hammer: You have the materials to craft this DIY at a workbench
• Basket: You have one (or more) of these items in your pockets
• Checkmark: You have crafted this recipe at least once (Which is relevant for certain Nookmile achievements, I believe)

Additionally, the recipes will have backgrounds that match the general kind of materials you need to make them. For example:

• Green: Plants / weeds
• Brown: Wood
• Grey: Iron Nugget
• White: Other (e.g. bait / medicine)