In the past, before the implementation of SEVIS, D/S had to be "determined" or "declared" but now it is tracked in a computer database and when you fall out of status, it is an identifiable date as reported by the school's DSO. If a school fails to report, it gets in serious trouble and loses its SEVIS status, so they do a much better job of reporting than they used to do. And the school's that don't follow the rules end up in the headlines, like TVU and UNVA. When a school loses SEVIS status it looses MONEY and the MONEY is more important to them than any particular student.
8 CFR § 214.2 Special requirements for admission, extension, and maintenance of status.
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(f) * * *
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(5) * * *
(i) General . Except for border commuter students covered by the provisions of paragraph (f)(18) of this section, an F-1 student is admitted for duration of status. Duration of status is defined as the time during which an F-1 student is pursuing a full course of study at an educational institution approved by the Service for attendance by foreign students, or engaging in authorized practical training following completion of studies, except that an F-1 student who is admitted to attend a public high school is restricte d to an aggregate of 12 months of study at any public high school(s). An F-1 student may be admitted for a period up to 30 days before the indicated report date or program start date listed on Form I-20. The student is considered to be maintaining status if he or she is making normal progress toward completing a course of study.