This Emoji means “prohibit, restrict or forbid” in Japanese.
CJK Ideographs are characters used in Chinese, Japanese and Korean languages. Their writing systems all completely or partly use Chinese characters.
📅 Japanese “Prohibited” Button was approved as part of Unicode 6.0 in 2010
under the name “Squared CJK Unified Ideograph-7981”
and added to Emoji 1.0 in 2015.