Seasons SimGuru/Maxis-Sourced Info

Holidays and the Calendar

Calendar and Holiday Celebrations: Mark your calendar for traditional holidays and create your own! Gather friends and family to celebrate holidays complete with traditions, gifts, and special guests.- blog post

https://twitter.com/SimGuruGeorge/status/1003777713063071744

https://twitter.com/SimGuruGrant/status/1004873542431731712

https://twitter.com/SimmingFan4000/status/1006288709015261186
https://twitter.com/SimGuruGeorge/status/1006292891185000448

Built-In Holidays

Decorate your home and bring Sims together to celebrate heartfelt holiday traditions. Ring in the new year with a celebration, enjoy a romantic date during Love Day or gather the family for a bountiful harvest feast. Watch as your Sims count down the calendar days until Winterfest, where presents are gifted, decorations are hung, and Father Winter pays a visit. - Origin

Blog Post featuring Harvestfest: https://www.ea.com/games/the-sims/the-sims-4/pc/news/the-climates-part-1

Harvestfest is in the fall, when Sims gather their closest friends and family for the grand meal. Sims can decorate their home for this special day, throw a turkey in the oven, and cook up some delectable goodies for the whole brood. Looking for an extra guest to join the gathering? You may find yourself encountering a certain straw-filled friend made especially for your garden.

When winter blows into town, so does Winterfest! Customize homes with a holiday pack and decoration box, give gifts, sip hot cocoa, and so much more. You won't want to miss a special visit from Father Winter. He'll be sure to brighten any Sim's holiday spirit. - blog

https://twitter.com/SimGuruGeorge/status/1003157814917791746
https://twitter.com/SimGuruGeorge/status/1004893661291675648

More on Winterfest!
https://twitter.com/SimGuruGeorge/status/1003775446004011009
https://twitter.com/SimGuruGeorge/status/1003776341144002561
https://twitter.com/SimGuruMegs/status/1004782975383293952
https://twitter.com/SimGuruGeorge/status/1006227727140057089

On gift-giving:
https://twitter.com/SimGuruGeorge/status/1003776945782337537
https://twitter.com/SimGuruGeorge/status/1004220120812609537
https://twitter.com/SimGuruGrant/status/1006215355939749889

https://twitter.com/kyrpronitemagic/status/1004848355011252224
https://twitter.com/SimGuruGeorge/with_replies

https://twitter.com/SimGuruMegs/status/1004777530820136960
https://twitter.com/SimGuruGeorge/status/1005446287712382978

Any holiday can be cancelled/deleted:
https://twitter.com/SimGuruGeorge/status/1004456142582378496

Birthdays
https://twitter.com/SimGuruEmory/status/1005873383987269632

Pre-Seasons Events
I clarified this as well with a Simmer on Reddit. If you start an event via the phone, nothing is different. If you want to schedule an event, start with the calendar not the phone:
https://twitter.com/SimGuruGrant/status/1005623006360526848

Custom Holidays
https://twitter.com/SimGuruKate/status/999778853043060736

https://twitter.com/oneorafael/status/1002273299693436928
https://twitter.com/SimGuruEmory/status/1002307505706262528

https://twitter.com/SimGuruEmory/status/1004432327856930816
https://twitter.com/SimGuruGeorge/status/1004502114863742976
https://twitter.com/SimGuruGeorge/status/1004613418962149376
https://twitter.com/SimGuruEmory/status/1004823781028687873
https://twitter.com/SimGuruGeorge/status/1004800885333999617
https://twitter.com/SimmingFan4000/status/1006299357732311040
https://twitter.com/SimGuruGeorge/status/1006305304290648065

There's some Spooky Stuff integration:
https://twitter.com/SimGuruGeorge/status/1004800323813195776
https://twitter.com/SimGuruGeorge/status/1005446287712382978
https://twitter.com/SimGuruGeorge/status/1008055074260594688

https://twitter.com/Goddess_Kalypso/status/1006291537557446656
https://twitter.com/SimGuruGeorge/status/1006293213370433536

https://twitter.com/Jordan12909286/status/1006272813668470785
https://twitter.com/SimGuruGeorge/status/1006279681350426625


Available Holiday Traditions

https://twitter.com/SimGuruMegs/status/1004775341028716545
https://twitter.com/SimGuruMegs/status/1004780954966036480
https://twitter.com/SimGuruGeorge/status/1004898532208201728

Some are:
https://twitter.com/SimGuruGeorge/status/1004497418178551808
https://twitter.com/SimGuruGeorge/status/1004538668453785600
https://twitter.com/SimGuruGeorge/status/1004611364105568257
https://twitter.com/SimGuruMegs/status/1004783836025110528
https://twitter.com/SimGuruGeorge/status/1004782528526409728
For more, see the trailer from June 7!

From the livestream*:

• sentient gnomes are back in the form of a holiday tradition. And they can get mad
  

Surprise Holidays
https://twitter.com/SimGuruGeorge/status/1004604820911607808

The Calendar
https://twitter.com/SimGuruEmory/status/1002652105352441856

To kick things off, one of the most significant features of this expansion pack is the calendar. So, let's talk about it! The calendar includes all upcoming holidays. Each one includes traditions to complete that make progress toward your Sim having an awesome time celebrating. Plus, predicted weather conditions can help Sims plan ahead. You'll also see the schedule of your Sim's household while checking out the calendar, including when they have to go to work. And to make even more planning possible, Sims' birthdays will be featured on the calendar. Pop open some nectar (for New Year's, that is) because all this and more will be in one place. Now that's an organized Sims game. - blog

https://twitter.com/Sindel1011/status/1003701102439694336
https://twitter.com/SimGuruEmory/status/1003705869974900737
https://twitter.com/SimGuruEmory/status/1003689611699224576
https://twitter.com/SimGuruEmory/status/1003690191326834688

https://twitter.com/SimGuruEmory/status/1004467707612311553
https://twitter.com/SimGuruEmory/status/1004467707612311553
https://twitter.com/SimGuruGeorge/status/1004500214961455104

The calendar week starts Sunday:
https://twitter.com/SimGuruGeorge/status/1004808820906835973

Connections with Other Packs
https://twitter.com/SimGuruGeorge/status/1006229663142707200
https://twitter.com/SimGuruEmory/status/1006518495792644096
https://twitter.com/SimGuruEmory/status/1004431487335161856
https://twitter.com/SimGuruEmory/status/1005102692513898503

https://twitter.com/SimGuruEmory/status/1006696022502854656

*Thanks to @icmnfrsh for livestream info.