在說或?qū)懸痪湓挄r，通常要選擇一個中心時態(tài)，這個中心時態(tài)影響其它時態(tài) ，即時態(tài)要前后一致。
    以“現(xiàn)在”為中心：若開始敘述或描述著眼于“現(xiàn)在”，則常以“現(xiàn)在”為起點(diǎn)，從而會出現(xiàn)一般現(xiàn)在時、現(xiàn)在進(jìn)行時、現(xiàn)在完成時或一般將來時連用的情況。
    Our postman usually delivers our arrival at 7 every morning. It (be) nearly lunchtime and the mail still (not arrive). I (suppose) the mail (come) soon. Perhaps he (be) ill. (is, hasn’t arrived, suppose, will come, is
    以“過去”為中心：若著眼于“過去”，則常以“過去某時”為基點(diǎn)，從而出現(xiàn)一般過去時、過去進(jìn)行時、過去將來時和過去完成時連用的情況。
    We lived in the street. They (build) houses all around us then. We (be) there for 10 years and (imagine) we (stay) there for the rest of our lives. (were building, had been, imagined, would stay)