昨天是星期天，不是星期六。

Yesterday was Sunday, not Saturday.

Source: Tatoeba

Sentence Composition

1 昨天 zuótiān yesterday
=2 是 shì
  1. to be (followed by substantives only)
  2. correct; right; true
  3. (respectful acknowledgement of a command) very well
  4. (adverb for emphatic assertion)
=2 是 shì variant of 是 shì
=3 星期天 Xīngqītiān Sunday
=3 星期天 xīngqītiān Sunday
=4 不是 bùshì
  1. no
  2. is not
  3. not
=4 不是 bùshi fault; blame
=5 星期六 Xīngqīliù Saturday
=5 星期六 xīngqīliù Saturday