According to the search results, there are several holidays in October 2023. Some of the holidays are observed only in the United States, while others are observed worldwide. Here are some of the holidays that will be observed in October 2023:

• Columbus Day (October 9, 2023)
• Canadian Thanksgiving (October 9, 2023)
• Indigenous Peoples Day (October 9, 2023)
• Leif Erikson Day (October 9, 2023)
• World Post Day (October 9, 2023)
• Ada Lovelace Day (October 10, 2023)
• World Mental Health Day (October 10, 2023)
• National Coming Out Day (October 11, 2023)
• Bosss Day (October 16, 2023)
• Sweetest Day (October 21, 2023)
• Halloween (October 31, 2023)

Note that this is not an exhaustive list, and there may be other holidays observed in October 2023 that are not mentioned here.