when was doing是什么時(shí)態(tài)

when was doing是一般過去時(shí)。
doing
v. 做；干（do的ing形式）
n. 活動(dòng)；所作所為
例句：
What on earth are you doing?
你究竟在干什么？
Shes doing a terrific job.
她活兒干得真棒。