Confusion regarding US passport stamp and period of admission

As best I can tell from the photo, you are misreading the stamp. There are two stamps:

• The normal admission stamp showing you entered the US in B-2 status on March 27 and are admitted for the usual six months, until September 26
• A second stamp across the face of the visa foil to mark your visa as used, which is just the normal admission stamp showing March 27

I cannot see a stamp that say April 27. In particular, I can clearly make out the letters "AR" in the month section of the second stamp, which would not be there if it said "APR" for "April." Because of the fold of your passport, the letter "M" is missing from "MAR" for "March." This stamp has no particular extra meaning.

As such, you were admitted on March 27th for six months duration.

It's always a good idea, as phoog recommends, to check your electronic immigration record at i94.cbp.dhs.gov, to confirm that you were admitted for six months.

It's worth mentioning that you could face further questioning on future trips to the US if you use your visa in a significantly different way than what you said your intentions were. If you said you were coming to the US for a week to attend a conference, and then actually stay six months, you might be asked to explain the reason for this.

That's very common. They have the stamp marked for 6 months from today's date and they stamp all passports the same, unless exceptions.

They ask you for long are you going to stay in the US to make sure you're not going to work and sounds reasonable for the reason you're going. If everything is OK, they stamp with 6 months.

I'm sure you can stay there until Sept 26 at midnight.

One exception when they do not mark the 6 months is for example (this happened to me), when you go out of the US and come back in. For example:

• 3 months in the US
• Leave for one week to Canada/Mexico
• Return to the US

In my case, I stayed for 5 months in total. 3 months before and 2 months after a short trip to Mexico.

Because many people leave the country for a few hours/days to extend their passport valid period (ie, 6 months + 6 months), when you return they might not want to extend your stay for another 6 months. In my case they stamped it with the initial 'Valid Until' they put the first time I went in.

Photo of my passport with 2 stamps and same date:

In general, to avoid any confusion regarding US passport stamp and period of admission, after every entry to the US it's advisable to download your electronic I-94 from the CBP website and keep it as a permanent record. Normally the electronic I-94 and the passport stamp should both show the same details:

• Date of Entry
• Class of Admission (which is usually the same as your visa type, in your case B-2)
• Admit Until Date

Since either the passport stamp or the electronic I-94 can be used as legal proof of your admission to the US, it's a good idea to make sure they're the same. This can also assuage any doubt in the case of ambiguity on the passport stamp.