I thought a timeline of the GF episodes would be nice
F-5-25-12 Tourist Trapped
The twins would've had to get out of school a lot earlier than I ever did for the timeline to make any sense. Lucky bastards. It's safe to asssume they were already in Gravity Falls for a few, as Dipper would put it, "long boring days of doing the exact same routine". Let me know if you heard his voice there. I sure did. Anyways, they could've been around anywhere between a few days to a week before this episode took place. Makes plenty of time to make counterfeit money and wreck their futures. I honestly wonder how Stan's gonna explain to their parents why "County Jail" is mentioned on their permanent records. I chose the 25th because at the end off the episode Stan looked like he felt a little bad for not spending too much time with the twins at the end of the episode. It'd make sense if he'd suddenly decide to attend fishing season and put together a family bonding day literally the day after. Plus, the twins came back looking like they got hit by a friggin bus. At least he recognized that he needed to make it up to them.
SA-5-26-12 The Legend of the Gobblewonker
If Gravity Falls was following Oregon's Fishing Season, then this would be the proper date
F-6-1-12 to M-6-4-12 Headhunters
According to the GF wiki, Wax Stan would've been decapitated on the 2nd since it took place on a Saturday during a Waxing Gibbous Moon. I think this episode went through the course of 4 days. Friday is when they found the hidden room and Mabel spent the next few hours making the wax figure. There's no way Stan could've gotten the reopening together on the same day and get such good business; especially since Mabel would be exhausted after a hard days work. She already miraculously got it done in a day. Don't push it. Saturday June 2nd they had the reopening, and later that night wax Stan was decapitated. The twins spent the following day trying to solve the mystery. Either the funeral took place at like, 3 in the morning, or the twins were fighting the wax figures all night and it took that long for Stan and Soos to get their act together. Whatever was going on, the episode ended the following Morning on the 4th.
SA-6-19-12 to TH-6-14-12 The Hand That Rocks the Mabel
Dipper said it had been a week since he accused Toby. And this episode ran through the course of 6 days. Day 1 is spent watching Gideon at the tent. Day 2 is Mabel hanging out with Gideon in his dressing room and the roof of his warehouse. The next day he picks her up for the date on a white horse. Day 4, another date. Day 5 is where Dipper does Mabel's breakup for her. And Day 6 is where Gideon was able to quickly con Dipper into meeting him at the warehouse before attempting murder.
F-6-15-12 The Inconveniencing
SA-6-16-12 Dipper vs Manliness
S-6-17-12 Double Dipper
M-6-18-12 Irrational Treasure
T-6-19-12 The Time Traveler's Pig
W-6-20-12 Fight Fighters
TH-6-21-12 Little Dipper
F-6-22-12 Summerween
This is the Summerween date, as marked by Stan's Calendar. Wow I had a hard time dating the last 7 episodes so that this would make sense. I find it hard to believe any of them could've overlapped eachother. That'd be too stressful for the twins too handle, and it doesn't look like they were under any extra pressure of solving multiple mysteries at once.
SA-6-23-12 to M-6-25-12 Boss Mabel
the bet lasted 3 days
S-6-24-12 Candy Monster
It was pretty clear that Summerween wasn't too long ago, and Mabel seemed pretty tired there before her little motivation. Probably from running the shack. Doesn't explain why Soos thought the monster was Stan, but hey, it's Soos. Why question it?
T-6-26-12 Bottomless Pit!
Stan seemed pretty insistent on getting rid of those suggestion cards from the previous episode. I'm guessing most were from Mabel or even about Mabel. Plus it's plenty of time for that Truth Teeth incident to occur. Also, this is the episode that confirmed GF is taking place in 0'12 thanks to Tax Fraud.
T-6-26-12 Stan's Tattoo
I'm chose this date thanks to the date marked photos at the beginning of the short. I made it the same date as the Bottomless Pit thanks to no time having passed during the episode
The rest of the episodes could've occurred at any given day. They could've continued the day to day scheduling like the last few, or the monsters finally decided to give the twins a break and space it out. At the latest, Gideon Rises would've occurred in early July. The Hide-Behind would've happened before that since Dipper still got the book. Currently there are no direct signs of when the rest have taken place, so for now I'm just gonna leave it in the open. Hope you guys liked my attempt at creating this timeline