These coins were struck from 1949 through to current and the date is given by the year number of the appropriate dynasty from the characters in the lower half of the coin.
From 1949-1987 the characters will be Showa Dynasty written as 昭 和 followed by the year number, which began counting from 1925. So 1959 for example would be “Showa year 34”, written as 昭 和 三 十 四 年 like this:
That continued until the Heisei Dynasty which began counting from 1988, and is written as 平 成 followed by the year number for that dynasty. Yours is 五 年 meaning “year five” so it’s 1993, like this: