Q. How do I obtain dates of entry into the United States?
A. Information regarding entry into the United States in or after 1982 is available from the U.S. Customs and Border Patrol (CBP). You may access the CPB's Freedom of Information Act web site here. Please note, however, that CPB is likely to deny any FOIA request concerning a third party without that person's written consent.
If you are a nonimmigrant alien and interested in obtaining evidence of your entry into the United States (I-94 Form), you may do so online here.
The National Archives and Records Administration maintains immigration records, more popularly known as "ship passenger arrival records," for various ports for the years 1800-1959. Click here for additional details.
I hope this information is helpful.