From Longman Dictionary of Contemporary English... at a time... at a timea) if someone deals with things one, three, ten etc at a time, they deal with them separately or in groups of three, ten etc If you raise your hands, I’ll answer questions one at a time. Frank took the stairs two at a time. b) if something happens for hours, days, months etc at a time, it continues for several hours, months etc Because of his work, he’s often away for weeks at a time. → time
Examples from the Corpus
... at a time• At times he was struck by a fierce desire to believe that the suspicion was nothing but a demon in his head.• At times whole sections will be finished while others remain blank.• At a time when skills are in demand, they have been wantonly discarded.• I don't think that I can send you more than four or five canvases at a time because of the cold.• They are evolving at a time when more and more consumers are turning to the Internet for their shopping needs.• I long, at times, for clear-cut answers.• In a way, she had come close to hating Nona at times, although she was not going to admit it.• The slow hours seemed to tick by one tick at a time in the night. 