Вот бы завтра был выходной.

Вот бы is a common Russian way to express a wish, similar to if only... or I wish... in English.

So:

• Вот бы завтра был выходной. = If only tomorrow were a day off.
• It often sounds emotional, dreamy, or hopeful.

The word вот by itself often means something like here is, there is, or look, but in вот бы it forms a fixed wish-expression and should be learned as a chunk.

This is one of the most common things learners notice.

In Russian, unreal or wished-for situations are often expressed with:

• бы
• plus a past-tense form

So even though the meaning is about the future, Russian uses the past form был to express something hypothetical or desired.

That is very similar to English in sentences like:

• I wish tomorrow were a day off
• If only tomorrow were a day off

So был here does not really mean simple past time. It is part of a wish/irrealis structure.

It is perfectly normal for бы to appear earlier in the sentence.

Russian бы is a little flexible in position. It often comes after the first stressed or important word/group rather than directly after the verb.

So these are related patterns:

• Вот бы завтра был выходной.
• Вот завтра был бы выходной.
• Если бы завтра был выходной...

In your sentence, вот бы is a very natural fixed opening for a wish. So the бы is already doing its job there, and it does not have to be repeated after был.

Because был agrees with выходной, which is masculine singular.

Russian past-tense forms change for gender and number:

• был — masculine
• была — feminine
• было — neuter
• были — plural

Here, выходной means day off and is grammatically masculine, so:

• был выходной

Even if the speaker is female, the sentence still uses был, because the verb agrees with выходной, not with the speaker.

Originally, выходной is an adjective, as in:

• выходной день = a day off / a non-working day

But very often Russian omits день and uses выходной by itself. In that case, the adjective is functioning like a noun. This is very common and natural.

So in your sentence:

• выходной = day off

You can think of it as a shortened version of:

• Вот бы завтра был выходной день.

But the shorter version is much more natural in everyday speech.

It is in the nominative singular masculine.

In был выходной, the word names what tomorrow would be: a day off. This is part of a predicate structure, and nominative is normal here.

So:

• выходной — nominative masculine singular

Yes, grammatically you can. It means the same thing.

But in normal speech, выходной by itself is more idiomatic and more common.

Compare:

• Вот бы завтра был выходной. — natural, everyday
• Вот бы завтра был выходной день. — understandable, but a bit fuller/heavier than needed

Most native speakers would prefer the shorter version.

Russian often does not use a dummy subject like English it or there.

English says things like:

• It would be nice if...
• There would be...
• Tomorrow would be a day off

Russian can simply say:

• Завтра был выходной.

No extra subject is needed. This is completely normal.

Yes. Russian word order is flexible, though different orders can sound more or less natural depending on emphasis.

Your sentence:

• Вот бы завтра был выходной.

is very natural and neutral for expressing a wish.

Other possible orders may shift focus:

• Вот бы был завтра выходной. — possible, but slightly different emphasis
• Завтра бы был выходной. — also possible, but вот бы is especially common for this kind of emotional wish

For learners, the safest version to remember is:

• Вот бы + time expression + past form + noun/adjective

It sounds natural and conversational. It is not slang, but it is definitely the kind of thing people say in everyday speech when expressing a wish.

It has a slightly emotional, wistful tone:

• If only tomorrow were a day off.
• Man, I wish tomorrow were a day off.

So it is normal in spoken Russian and informal writing.

They are close, but not exactly the same in feeling.

• Вот бы завтра был выходной. = a direct wish: If only tomorrow were a day off
• Если бы завтра был выходной... = literally If tomorrow were a day off..., which usually sounds like the beginning of a larger conditional thought

So:

• Если бы завтра был выходной, мы бы поехали за город.
  If tomorrow were a day off, we would go out of town.

By itself, Если бы завтра был выходной can still sound like a wish in conversation, but вот бы more clearly signals pure wishing.

Yes. Хорошо бы is another common way to express a wish.

Compare:

• Вот бы завтра был выходной.
• Хорошо бы завтра был выходной.

Both are natural. A rough difference is:

• вот бы — often a bit more emotional or spontaneous
• хорошо бы — often a bit calmer, like it would be nice if...

Both are useful and common.

Very literally, it is something like:

• Вот бы — if only
• завтра — tomorrow
• был — were / would be
• выходной — a day off

So a literal gloss would be:

• If only tomorrow were a day off.

A very word-for-word rendering like Here if-only tomorrow was day-off would sound strange in English, but it helps show the structure.

Yes. Here завтра means tomorrow as the day in question.

The sentence is about the status of tomorrow:

• Tomorrow would be a day off

So the idea is not tomorrow, I would have free time, but specifically tomorrow would be an off day / non-working day.

Yes, absolutely. It is a very natural sentence.

A Russian speaker might say it when:

• they have to work tomorrow
• they wish school were canceled
• they want an unexpected free day

It sounds like an ordinary, idiomatic way to express that wish.