The ideal time to start applying for the fall intake in the U.S., typically commencing in September, varies depending on several factors but generally follows a multi-stage timeline. 

Beginning about a year in advance i.e. 12-18 months prior, prospective applicants should initiate their research into universities and programs, register for any required standardized tests, and start crafting application materials like Statements of Purpose (SOPs) and Letters of Recommendation (LORs). This early stage also provides an opportunity to explore scholarship and financial aid options. 

As the timeline progresses to 9-12 months prior to the fall intake, applicants need to narrow down their choices, establish contact with potential advisors or professors where relevant, and ensure they are registered for standardized tests. They should also initiate drafting SOPs and essays and request LORs from their recommenders. 

In remaining 6-9 months, applicants should closely monitor application deadlines, complete online applications, and verify that all required documents, including transcripts and test scores, are submitted. During this phase, SOPs and essays should be meticulously revised and finalized, and applicants should follow up with recommenders to confirm timely LOR submissions. 

During final months leading up to the fall intake, once applicants receive admission decisions and has finalized a university, they apply for student visas, arrange accommodation, and complete pre-departure requirements.