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但是上面(a)(4)说physically present in the United States for at least 30 months of the five years preceding the date of filing the application，那么从今天倒推5年，如果从2010年3月算起，我的physical presence就满30个月了。
-It is from the date you got the green card.

请问可以这么算吗？

还是必须从拿到绿卡后算。
-Right. The  "preceding the date of filing the application" here means "before the date you file N-400 ". If you file N-400 now, it will be rejected or denied. USCUIS is very strict  and picky in US citizenship application.