据马红军《翻译批评散论》将midmorning理解为“上午十点左右”，“midafternoon”理解为“下午三点左右”，大体上是不错的。

我查了一下，midmorning：The middle of the morning.

it is based around the working morning which is usually 9 am (in most cases),

见：https://www.answers.com/Q/What_time_is_mid_morning

late morning:

What does late morning mean? - Quora

https://www.quora.com/What-does-late-morning-mean

The phrase is usually in reference to an eight-hour workday, so assuming the start time is eight o’clock inthe morning, mid-morning would be ten o’clock, and anything between ten and noon would be late morning.

midafternoon：the part of the afternoon centering approximately on three o'clock; the period approximately halfway between noon and sunset.

lateafternoon是什么时间呢？

There is no precise definition of late afternoon, except that it is the part of the day that is just before evening time. Oxford Dictionaries defines afternoon as the time between noon or lunchtime until evening.对于下午晚些时候没有确切的定义，除了它是一天中刚好在晚上时间之前的那一部分。牛津词典将下午定义为中午或午餐时间到晚上之间的时间。

Cambridge Dictionaries Online states that afternoon is from about noon or after the midday meal until about 6 p.m. or when the sun begins to go down. In Middle English, the word for afternoon was "aftermete," which means "after the noon meal." Given the variations in mealtimes and the times of sunset, the period of late afternoon is difficult to define. The term "late afternoon" can sometimes substitute for the word "evening."剑桥在线词典指出，当天下午是从中午或中午饭后到下午6点左右或太阳开始下山。在中古英语中，下午这个词是aftermete，意思是“午餐后”，由于午餐时间和日落时间的不同，很难定义午后的时间段。“下午晚些时候”这个词有时可以代替“晚上”这个词

https://www.reference.com/science/time-considered-late-afternoon-b95c198cd015828f

afternoon和evening大致的时间划分：

What time of the day is considered as afternoon and evening?

https://www.answers.com/Q/What_time_of_the_day_is_considered_as_afternoon_and_evening