Holidays and Observances
Alphabetical Listing of O Holidays

Below, you can find a Holidays and Observances Alphabetical Listing of US Holidays and World Holidays and Observances that start with O. We will add any new Holidays as we find them!  

 

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Organic Harvest Month is the Entire Month of September! I've been growing my own Organic Vegetables over the last couple of years. Not only does it save a lot of money, but there is nothing better than going outside to pick stuff for dinner! This was one day's haul - with this many tomatoes, I took off the skins and ran everything through my juicer.  I was then able to freeze the juice/pulp in freezer quart size bags which are perfect for taking out to make pasta sauce or any type of soup. For excess zucchini - I peeled them and just grated them and put in freezer baggies to add to soups and sauces.

O Holidays and Observances

• O. Henry Pun-Off Day - May 9, 2026

• Oatmeal Cookie Day - May 18

• Oatmeal Monday - February 9, 2026 (Second Monday in February)

• Oatmeal Month - January

• Oatmeal Nut Waffles Day - March 11

• Obesity Awareness Month (Adults) - September

• Obesity Care Week (OCW) - March 2-6, 2026 (First Week of March)

• Obesity Prevention Awareness Week - September 1-7

• Observe the Weather Day - January 25

• Occult Day - November 18

• Occupational Safety and Health Professionals Day - May 6, 2026

• Occupational Therapy Day - October 27

• Occupational Therapy Month - April

• October Holidays - If you just want a quick bulleted list of all the October monthly holidays, along with the complete schedule of weekly and daily holidays for this month, head over to our main October Holidays page.

• October Monthly Holidays - Looking for more than just a list? We have created a complete guide breaking down the meaning, history, and wellness themes behind every single month-long observance in October.

• Odd Day - November 9, 2026 (Last one was 9-11-13 - three consecutive odd numbers)

• Odd Socks Day - September 17, 2026 (in Australia) 

• Odie Day - August 8 (Garfield's Friend)

• Office Chocolate Day - October 20

• Official Lost & Found Day - December 11, 2026 (Second Friday in December)

• Oglethorpe Day - February 12

• OK Day - March 23
  

• Oklahoma City Bombing Commemoration Day - April 19

• Oklahoma Day - April 22

• Okra Month - June

• Oktoberfest - September 19, 2026 - October 4, 2026 Beer Festival in Munich, Germany. This festival is now held all over the World. Also, check out our Holidays in Germany page!

• Old Clem's Night - November 23

• Old Farmers Day - October 12

• Old Inauguration Day - March 4

• Old Maid's Day - June 4

• Old New Year's Day - March 25
  

• Old Rock Day - January 7

• Old Time Fiddlers Week - June 21-27, 2026 (Third Week in June)

• Old Time Player Piano Day - May 27

• Old Time Player Piano Weekend - May 21-24, 2026 (Memorial Day Weekend)

• Older Americans Mental Health Week - May 24-30, 2026 (Last Full Week in May)

• Older Americans Month - May

• One Boston Day - April 15

• One Day Without Shoes Day - May 10

• One-Liners Day - January 21

• One-on-One Month - September

• One Voice Day - July 26

• Onion Month - August

• Open that Bottle Night - February 28, 2026 (Last Saturday in February)
  

• Opera Day - February 8

• Operating Room Nurse Awareness Week - November 8-14, 2026

• Operating Room Nurse Day - November 14

• Operation Iraqi Freedom Day - March 19

• Operation Red Wings Observance - June 28

• Operation Safe Driver Week - July 12-18, 2026

• Operation Santa Paws - December

• Opposite Day - January 25
  

• Optimist Day - February 5, 2026 (First Thursday of February)

• Orange Chicken Day - July 15

• Orangemen's Day (Also known as Glorious Twelfth and The Twelfth) - July 12

• Orange Month - August
  

• Orange Shirt Day - September 30

• Orangemen's Day - July 12

• Oranges and Lemons Day - March 19, 2026 (Third Tuesday in March)
  

• Orangutan Caring Week - November 8-14, 2026

• Organic Beer Fest - June 25-27

• Organic Harvest Month - September

• Organize Your Home Day - January 14

• Organize Your Home Office Day - March 10, 2026 (Second Tuesday in March)
  

• Organize Your Medical Information Month - October

• Origami Day - November 11

• Orphan Sunday - November 8, 2026 (Second Sunday in November)

• Orthodox Christmas Day - January 7

• Orthodox Easter - April 12, 2026 

• Orthodox Easter Monday - April 13, 2026
  

• Orthodox Forgiveness Sunday - February 22, 2026

• Orthodox Good Friday - April 10, 2026

• Orthodox Green Monday - February 23, 2026

• Orthodox Holy Saturday - April 4, 2026
  

• Orthodox Holy Week - March 29, 2026 - April 4, 2026 

• Orthodox Lent - February 23 - April 4, 2026

• Orthodox Meatfare Sunday - February 15, 2026

• Orthodox New Year - January 14
  

• Orthodox Palm Sunday - April 5, 2026

• Orthodox Pentecost - May 31, 2026

• Oscar the Grouch Day - June 1

• Ostara - March 20, 2026 (Spring Equinox) 

• Osteoporosis Prevention Month - May

• Ovarian Cancer Awareness Month - September

• Own Business Day - October 13, 2026 (Second Tuesday in October)

• Own Your Own Home Day - January 21

• Own Your Share of America Day - June 15, 2026 (Closest Weekday to June 14)

• Oyster Day - May 5

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A, B, C, D, E, F, G, H, I, J, K, L, M, N, N-Pg2 O, P, Q, R, S, T, U, V, W, X-Y-Z