White Day 2018 is on March 14. The day is celebrated in Japan one month after Valentine's Day. It is also observed in South Korea, Taiwan and China. In Japan, Valentine's Day is observed by females who present chocolate gifts , usually to a male, as an expression of love, courtesy or social obligation.
A handmade chocolate is usually preferred by the receiver, because it is a sign that the receiving male is the girl's "only one". On White Day, the converse happens: males who received a honmei-choco ("chocolate of love") or giri-choco ("courtesy chocolate") on Valentine's Day are expected to return the favor by giving gifts, usually more expensive.
Traditionally, popular White Day gifts are cookies, jewelery, white chocolate, white lingerie and marshmallows. Sometimes the term sanbai gaeshi ("thrice the return") is used to describe the generally recited rule that the return gift should be two to three times the cost of the Valentine's gift.
White Day was first celebrated in 1978 in Japan. It was started by the National Confectionery Industry Association as an "answer day" to Valentine's Day on the grounds that men should pay back the women who gave them chocolate and other gifts on Valentine's Day. (From: WIkipedia)