The calendar that is formally used in Iran is called Persian Calendar(or the Solar Hijri calendar). It is not an exaggeration to say that Persian Calander is one of the world's most exact calendar systems. The Solar Hijri calendar should not be confused with the Islamic calendar (or Hijri calendar) utilized in many Islamic countries and by Muslims around the globe.
The Persian Calendar is a solar calendar, signifying that its time calculation is formed on the Earth's movements around the Sun.
Unalike the Gregorian calendar system that goes along with a set of pre-arranged rules to stay in sync with the solar year, the Persian Calendar is based upon astronomical observations. The year starts at midnight nearest to the vernal equinox in Iran. The first day of the New Year is called Nowruz, and it’s celebrated around the globe by Iranian peoples.
There are several religious and national holidays in the Persian Calendar. Here is the list of holidays for this year. The highlighted ones in red are of those that tourist sites and museums are closed.