在一天的最后
at the latest time in the day
I'll switch on the washing machine last thing so it'll be finished when I get up in the morning. 晚上睡觉前我会开启洗衣机，这样等我早晨起床后衣服就洗好了。
You should avoid drinking coffee last thing at night.
I do my exercises first thing in the morning and last thing at night.
He usually calls me last thing, just before he goes to bed.
It's not a great idea to have difficult conversations last thing.
See also: last adjective adverb pronoun noun