Bismillah al-Rahmaan al-Raheem
Although the day of Nowruz (which is the first day of the solar Hijri year) does not have any authentic Islamic and shar'i basis, celebrating it is not a problem. But is a good and positive thing that this day is used as an excuse for families to get together and visit each other (as is the norm in the Islamic Republic of Iran), as this is sile rahm (strengthening ties with family members) and is in itself a recommended action. Also, the 'ibaadaat that have been specified for this day can be performed with the intention of rajaa' (i.e. with the hope that Allah will accept).