Nowruz, meaning 'New Day' is the traditional ancient Iranian festival and also the start day of Iranian "New Year" .Also, It is the beginning of the new year for the people of Afghanistan, Azerbaijan and Tajikistan.
Nowruz is celebrated and observed by Iranian peoples, Kurdish People and has spread in many other parts of the world, including parts of Central Asia, South Asia, Northwestern China, the Crimea and some ethnic groups in Albania, Bosnia, Serbia and the Republic of Macedonia.
Nowruz marks the first day of spring and the beginning of the year in Iranian calendar. It is celebrated on the day of the astronomical vernal equinox, which usually occurs on March 21 or the previous/following day depending on where it is observed. The moment the Sun crosses the celestial equator and equalizes night and day is calculated exactly every year and Iranian families gather together to observe the rituals.
The term Nowruz in writing, first appeared in Persian records in the second century AD, but it was also an important day during the time of the Achaemenids (648-330 BC)
The UN's General Assembly in 2010 recognized the International Day of Nowruz, describing it a spring festival of Persian origin which has been celebrated for over 3,000 years. During the meeting of The Inter-governmental Committee for the Safeguarding of the Intangible Heritage of the United Nations, held between 28 September – 2 October 2009 in Abu Dhabi, Nowrûz was officially registered on the UNESCO List of the Intangible Cultural Heritage of Humanity. Since 2010, the United Nations General Assembly recognizes March 21 as the "International Day of Nowruz". On 15 March 2010, The United States House of Representatives passed The Nowruz Resolution (H.Res. 267), "Recognizing the cultural and historical significance of Nowruz.
The most significant sign of Nowruz in Iranian houses, is Haft Seen (seven articles with their names beginning in Persian with the letter "S" [Seen]) conjoining with a mirror, candles, incense burner, bowl of water with live gold fish, the plates and vessels with green sprouts, flowers, fruits, coins, bread, colorfully painted boiled eggs like "Easter eggs and so on.
The usual things with "S" are:
First Plate: SERKEH, the vinegar, Which adds taste to the things you want to preserve and relish. It symbolizes tasty preservation.
Second Plate: SUMAC, exotic in its own way, It makes kebabs have a tangy taste, a taste you relish. It symbolizes taste.
Third Plate: SIR, garlic. Some may not like its aroma and others love it. It lowers blood pressure. It pacifies. It symbolizes peace.
Fourth Plate: SAMANU, a sweetish paste, made from germinating wheat. It symbolizes the sprouting spring, the time for happy growth.
Fifth Plate: SIB, apple. It symbolizes the fruits of our world, both literally and allegorically.
Sixth Plate: SENJED, the jujube fruit of the sorb tree. It is the fruit of a tree which provides shade in summer. It symbolizes the shelter and security you need when you want a rest.
Seventh Plate: SABZI, fresh green herbs. It comes from green fields. It symbolizes prosperity.

New Year holidays long last for two weeks.