Example from Minna No Nihongo:

Lesson 4 : **あした** 6 時に起きます。

Lesson 9 : **きょう** **は** 早く 帰ります。

Why is は sometimes used with such a time words and sometimes not?
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2020-05-29T16:47:45.103
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2020-05-30T15:49:15.287
2020-05-30T10:52:29.037
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question
grammar particle-は word-usage
When do i use は for きのう,きょう,あした?
* As in many other situations 'は ha/wa' can denote a special significance this time. For example あした 6 時に起きます。plainly states that the subject of the sentence will wake up at 6 tomorrow. 
  * For the other example, きょう は 早く 帰ります。 there is a 'は ha/wa' inserted so it would add a nuance that I am waking up early today AND that this is not common for me to do this, i.e. normally I would wake up later.

In spoken English you might accentuate the "Today" as in "TODAY, I'm waking up
early."
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2020-05-30T12:52:00.920
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2020-05-30T12:52:00.920
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answer
は:

  1. Denotes the topic.

  2. For comparing, emphasis

So in your second example

> きょう は 早く 帰ります。

You wanna emphasize **TODAY** , you may always go back home late, but not
today.
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2020-05-30T15:49:15.287
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answer