Both "January 1" and "January 1st" are correct ways to write the date. However, they have slightly different uses:
- January 1: This is the most common way to write the date in formal writing, such as in documents, articles, and official communications.
- January 1st: This is more common in informal writing and speech. It is often used when referring to a specific event or celebration that occurs on that day, like New Year's Day.
Ultimately, both forms are acceptable, and the choice depends on the context and your personal preference.