Expiration Date of Entry Visa
The validity period shown in a non-immigrant visa relates only to the period during which it may be used in making application for admission into the United States; it does not indicate the length of time one may spend in the United States. Some visas are valid for several years, while others are valid only for a few months or weeks. The visa stamp in your passport allows you to enter the United States and may expire after your arrival in the country. Once you have entered the United States to begin your studies, you will be concerned with this particular expiration date only when you expect to travel outside the U.S. If you wish to re-enter the country and your visa has expired, you must apply for a new entry visa at a U.S. consulate or embassy abroad (except when traveling to Canada. See note about Travel to Canada). Entry visas are issued only outside the U.S. You must consult with the Office of International Recruitment and Admission before traveling outside of the United States (see Travel Abroad).
D/S: Duration of Status notation
The F-1 or J-1 student is admitted to the United States for "duration of status," noted as "D/S" on both Form I-20 or DS-2019 IDs. Duration of status means the period during which the student is pursuing a full course of study in any educational program (e.g., BA) and any periods of authorized practical training, plus sixty days (F-1) or 30 days (J-1) within which to depart from the U.S. or apply for a change of status. The Form I-94 should be printed and kept with your other documents, since it indicates the purpose of admission and the length of time for which his or her stay is authorized. Students should also always have with them their Form I-20 or DS-2019, particularly when they travel, even within the United States, since this is their personal identification and carries their computerized "Admission Number." A non-immigrant who remains in the U.S. beyond the period for which he/she has been granted permission to stay may become subject to deportation.
Extension of Stay
All international students should pay attention to their approved length of stay in the U.S. The length of authorized stay for F-1 and J-1 individuals is indicated on the I-94 print out as D/S (duration of status), and refers to item 5 on the I-20 and to item 3 on the DS-2019. People who need additional time to complete their degree requirements must consult with the Office of International Recruitment and Admission at least 30 days prior to the expiration of their authorized length of stay.