Could I ask, it is possible to use present perfect tense in a case when I don't have an exact time definition? Let me explain my statement. This is a classical example from book. She has been mentally ill since my birth. However, I would like to ask whether it is possible to emphasize that it started from an exact past moment and continues to present. Like: Every woman: I used to be fine. However, in 20XX I had a baby and left the job. I don't know what happened to me, but I have been mentally ill.(since my baby's birth and also in present) However, I don't want to mention since my baby's birth. A listener/reader has to read this not said/written part from the context. Thank you.