Dziś wieczorem nie mam czasu na obejrzenie filmu.

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Breakdown of Dziś wieczorem nie mam czasu na obejrzenie filmu.

• mieć: to have
• wieczorem: in the evening
• nie: not

Questions & Answers about Dziś wieczorem nie mam czasu na obejrzenie filmu.

Why is there no word for I in this sentence?

Because Polish usually drops subject pronouns when they are clear from the verb form.
Here, mam means I have, so ja is unnecessary.

• mam = I have
• nie mam = I do not have

You could say Ja dziś wieczorem nie mam czasu..., but that would add emphasis, like I don’t have time tonight.

What does Dziś wieczorem mean exactly? Why are there two time expressions?

Dziś wieczorem means this evening or tonight.

The two words work together:

• dziś = today
• wieczorem = in the evening

So together they narrow the time down to the evening of today.

Why is it wieczorem and not wieczór?

Because wieczorem is the form used adverbially to mean in the evening.

• wieczór = evening as a noun
• wieczorem = in the evening

This is a very common pattern with parts of the day in Polish. In this sentence, wieczorem is not the subject or object; it functions more like a time adverb.