Whether you’ve decided to apply to grad school, already started, or have no idea at all, it’s good to keep in mind the approximate deadlines for most graduate program deadlines. This depends on the school and department but for the most part the earliest deadlines are around Dec 1 and the latest deadlines can be up to end of Dec-even beginning of Jan. Check out the website for the department you’re interested in and write it down just to have a general idea.
A lot of the time Phd and Masters deadline can differ even for the same department so keep this in mind. For example, Berkeley’s statistics program has a deadline of Dec 15 for PhDs and Jan 6, 2022 for MAs. Also it’s a good idea to check with departments their deadlines regarding test scores and recommendation letters.