India, Sept. 2 -- September is shaping up to be a crucial month for US immigration applicants, with changes affecting green cards, H-1B workers, international students and immigrant visa applicants taking effect or moving closer to implementation.

Several developments have firm dates, while others remain proposals. For applicants, the distinction matters: some changes require immediate action, while others are still moving through the regulatory process.

International students face another major change on September 15, when DHS replaces the longstanding Duration of Status (D/S) system with fixed periods of admission for F students.

Under the new rule, F-1 students will generally be admitted for the length of their program listed on the...