All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is not permissible to fast on the day of doubt, which is the day that people doubt whether it is the 30th day of Sha'baan or the 1st day of Ramadan, because the Prophet forbade us from fasting this day.
'Ammaar Ibn Yaasir said: "Whoever fasts the day of doubt has indeed disobeyed Abul-Qaasim ." [Muslim, Abu Daawood and At-Tirmithi]
Besides, you should know that fasting Ramadan is dependent on the sighting of the moon, so whoever sees the moon he has to fast, otherwise he has to consider Sha'baan 30 days.
Finally, we draw your attention that Thursday is the 30th of Sha'baan this year, and we do not know whether this is the case there in America. So, in this matter, one has to refer to Islamic foundations which are entrusted regarding the sighting of the moon and seeking to find the beginning of the lunar months.
Allaah Knows best.