Indians would celebrate every day of the year, just give them a reason or a purpose: victories, historical events, harvesting, etc. But there is one grand and annual festival, which is of a whole different significance.
Maha Shivaratri is held annually in February–March. During the festival, devotees don't eat all day and don't sleep at night. The event which is also called 'Night of Lord Shiva' involves offering flowers and fruit to a deity, ringing bells in the temple, and offering prayers to god. But the most important tradition is presenting milk and leaves to the Lingam. That's how devotees pay homage to Shiva.
Moreover, those who recite the mantra on the day of Maha Shivaratri will be free of all sins, and women who pray on this auspicious day will attain a perfect husband and marital bliss in general.
Curd, clarified butter, sugar, honey, and milk are believed to symbolize immortality, so these five kinds of food are offered to Shiva as well.