Pig Days was a special advent calendar for Angry Birds Seasons released on July 3, 2014 (along with the update of South Hamerica).
It appeared on the South Hamerica Update. It only appears when you select the
Play Button. It can also appear if you're on Season 2010-2011, Season 2012, Season 2013, Season 2014, and Season 2015. It has ended in Summer Camp update and replaced with The Pig Challenge.
Pig Days - Page 1 1-1 (Apollo Moon Landing Anniversary). 1-2 (Comic Con). 1-3 ("AngryBirdsNest" Birthday). 1-4 (Leaning Tower of Pisa Anniversary). 1-5 (Lefthanders Day) 1-6 (Aviation Day) 1-7 (Beacon Day). 1-8 (Basketball Finals). 1-9 (Moon Festival). 1-10 (Video Game Day). 1-11 (Talk like a pirate day). 1-12 (Hobbit Day). 1-13 (International Coffee Day). 1-14 (World Egg Day). 1-15 (Columbus Day). The Pig Days Part 3
 From July 19, levels are unlocked from every specific day, and has each level with a different festive day. The first chapter has 15 levels and the second has 9 levels.
Chapter 1: v4.1.0
Sun. 20 July: Commemorates the 45th anniversary of Apollo 11's landing on the Moon
Thu. 24 July: Marks the Start of the San Diego International Comic-Con Convention
Mon. 28 July: Commemorates the 4th anniversary of AngryBirdsNest
Sat. 09 August: Commemorates the 841st anniversary of breaking ground on the Leaning Tower of Pisa
Wed. 13 August: Celebrates International Lefthanders Day
Tue. 19 August: Celebrates Aviation Day
Sat. 30 August: Celebrates Bacon Day
Sat. 06 September: Celebrates Basketball Finals
Tue. 09 September: Celebrates Moon Festival
Fri. 12 September: Celebrates Video Game Day
Fri. 19 September: Celebrates Talk Like A Pirate Day
Mon. 22 September: Celebrates Hobbit Day
Mon. 29 September: Celebrates International Coffee Day
Fri. 10 October: Celebrates World Egg Day
Mon. 13 October: Celebrates Columbus Day
Chapter 2: v4.2.0
Wed. 15 October: Celebrates Learn Code Day
Fri. 31 October: Celebrates All Hallows' Eve
Sat. 1 November: Celebrates All Hallows' Day
Sun. 2 November: Celebrates Day of the Dead
Wed. 5 November: Celebrates Guy Fawkes Night
Tue. 11 November: Celebrates Ahtisaari Days
Tue. 18 November: Celebrates William Tell Day
Fri. 21 November: Celebrates Hot Air Balloon Day
Thu. 27 November: Celebrates Thanksgiving
Thu. 11 December: Commemorates the 5th anniversary of Angry Birds (Bird Day)
Wed. 31 December: Celebrates NYE 2015
Fri. 2 January: Celebrates Sci-Fi Day
Tue. 13 January: Celebrates Rubber Duck Day
Mon. 19 January: Celebrates Popcorn Day
Wed. 28 January: Celebrates Data Privacy Day
Tue. 3 February: Celebrates Windmill Day
Chapter 3: v5.0.0
Sat. 14 February: Celebrates Valentine's Day
Mon. 16 February: Celebrates The Start of the 2015 "Rio Open"
Thu. 19 February: Celebrates Chinese New Year
Fri. 27 February: Celebrates Polar Bear Day
Tue. 3 March: Commemorates NASA 100YO anniversary (NACA Centenary)
Mon. 9 March: Celebrates the "Gold In California"
Tue. 17 March: Celebrates Submarine Day
Fri. 27 March: Celebrates Hanami
Fri. 3 April: Celebrates Easter
Sun. 12 April: Celebrates the "First Spaceflight"
Wed. 22 April: Celebrates Earth Day
Chapter 3 (cont.): v5.0.1
Fri. 1 May: Celebrates May Day
Tue. 5 May: Celebrates Cinco De Mayo
Wed. 13 May: Celebrates Leprechaun Day
Fri. 22 May: Celebrates World Goth Day
Fri. 29 May: Commemorates the End of Middle Ages
Thu. 8 June: Celebrates World Ocean Day
Fri. 12 June: Celebrates Magic Day
Fri. 19 June: Celebrates Midsummer's Eve
Thu. 2 July: Celebrates UFO Day
Tue. 14 July: Celebrates Pandemonium Day
Chapter 4: v5.0.1
Mon. 20 July: Commemorates Pig Days Anniversary
Thu. 30 July: Angry Birds 2 Out now!
Sun. 02 August: Celebrates Friendship Day
Sat. 08 August: Celebrates Cat Day
Tue. 11 August: Celebrates Play in the Sand Day
Sun. 23 August: Celebrates Ride The Wind Day
Sun. 30 August: Celebrates International Bat Night
Tue. 08 September: Celebrates International Literacy Day
Thu. 16. September: Celebrates Preservation of the Ozone Layer Day
Tue. 22. September: Celebrates Car Free Day
Chapter 5: v5.3.1
Thu. 22. October: Commemorates the 5th Anniversary of Angry Birds Seasons
Thu. 29. October: Celebrates Internet Day
Mon. 02. November: Celebrates All Souls' Day
Wen. 11. November: Celebrates Origami Day
Tue. 17. November: Celebrates Meteor Shower Day
Tue. 31. December: Celebrates New Year 2016
Sun. 10. January: Celebrates Crossing the Rubicon Day
Wen. 20. January: Celebrates Penguin Awareness Day
Mon. 08. February: Celebrates Chinese New Year 2016
Chapter 6: v6.0.0
Sun. 14. February: Celebrates Valentine's Day 2016
Sun. 28. February: Celebrates Polar Bear Day 2016
Wen. 02. March: Celebrates World Wildlife Day
Mon. 07. March: Celebrates Women's Day
Tue. 08. March: Celebrates Solar Eclipse
Fri. 18. March: Celebrates Earth Hour
Sat. 26. March: Celebrates Easter 2016
Chapter 7: v6.0.1
Fri. 01 . April: Celebrates April Fools
Sun. 10. April: Celebrates Golfer Day
Tue. 12. April: Celebrates First Spaceflight 2016
Thu. 21. April: Celebrates Loch Ness Day
Sun. 24. April: Celebrates World Penguin Day
Sun. 08. May: Celebrates Mother's Day
Thu. 12. May: Celebrates Anger Management (As part of the promotion for The Angry Birds Movie)
Fri. 13. May: Celebrates Pigs Arrive (As part of the promotion for The Angry Birds Movie; The day of most international releases)
Fri. 20. May: Celebrates The Eagle's Den (As part of the promotion for The Angry Birds Movie; The day of the U.S., Canada, and China releases)
Sun. 29. May: Celebrates First Ascent of Everest
Wen. 01. June: Celebrates World Milk Day
On the Pig Days map, a mooncake which has a candle on it is seen, so that event would mean it is in commemoration of "AngryBirdsNest" 4th birthday.
It is the second game that a Fat Pig appears outside of "Angry Birds Space" and the third appearance of " El Porkador!".
It is the second game to have alliteration in the background levels.
Ever since the Summer Camp update, Pig Days is located in the 2016 section, shows how many stars, coins, and feathers the player has achieved, and hasn't had a new level added since World Milk Day, indicating that it has ended.
New sprites and features
The Pig Days introduced some new sprites and/or features in Angry Birds Seasons:
1-1: Fire sprite. It used later in 1-7.
1-2: Wingman and El Porkador came from Angry Birds Friends, but Wingman lost his 'WHAM!' figures. - The 'ComPigCon' and 'ComBirdCon' posters. - Terence also equipped with a hard ball, chained to him.
1-6: Clouds now are 'out of the background' and can block your way.
1-8: Basketball and net. It used later in Ham Dunk episode, alongside net stander and and 'Dunk' bonus.
1-12: Barad-dûr Tower sun sign and flag.
2-2: Zombie pig costume.
2-5: Guy Fawkes clothes for pigs.
2-6: Minion Pigs are Playable, Cannons and Swords
2-8: The explosive King Pig golden sign.
2-9: Feathers and turkey skin.
2-12: Alien pig costume and floating object. It used later in Invasion of the Egg Snatchers episode.
2-13: Rubber Duck. It used later in Angry Birds 2 as Power-Up.
2-14: Popcorn and Shovel.
2-15: Fuse, Pickaxe, Scarf and Stop sign.
3-1: Big Red Ballon
3-2: Tennis Racket, Tennis Ball and Rio Open banner sign
3-5: Space Helmet and Wrench
3-12: Hats and Cow costume.
4-9: Straw House. It used later in Angry Birds 2 as First level.
4-10: Devil Rubber Duck.
5-9: Big Glass
6-2: Warning block.
Angry Birds Seasons Pig Days Weekly Levels!
Pig Days Trailer
Angry Birds Blog/Pig Days.
Angry Birds Nest/Pig Days Guide. ↑
Angry Birds Oficial site.