It means when.
Dan means to shoulder responsibility.
Explanation of Dan:
move
(Form and sound. From the hand, Zhan Sheng. Original meaning: shoulder-pick
homonym
Dan, what also. From the people, Zhan Sheng. With the back said negative, with the shoulder said. -- Shuowen. The word is also called \"Dan\".
Heavy, negative also. -- \"Zi Lin\"
Carry a bag to get paid. -- Cao Cao, \"Bitter Cold Walk\"
Take a book with you. -- War State Policy · Qin Cze I
Another example is: the shoulder can not carry, the hand can not lift; dandai
bear
Take your umbrella in China
Bear, undertake
My heart is sad. -- Qing · Lin Juemin, \"Book with My Wife\"
Take part in STH. To undertake (undertake); Take responsibility for; Help); Dudu (a person capable of taking responsibility); Dan Gan (Dan Gan Ji. Responsible)