Gắng đến đúng giờ.

Yes—here gắng means try, make an effort, or do your best.

It is closely related to cố gắng, which is the more common full expression for to try / to make an effort. In this sentence, gắng is a shorter, more compact way to say it.

So:

• Gắng đến đúng giờ. = Try to arrive on time.
• Cố gắng đến đúng giờ. = also Try to arrive on time.

For many learners, cố gắng will feel safer and more neutral.

Vietnamese often leaves out the subject when it is obvious from context.

In Gắng đến đúng giờ., the understood subject is usually you. So the full idea is:

• (Bạn) gắng đến đúng giờ.

But in natural Vietnamese, bạn is often omitted in short instructions, reminders, or requests.

Vietnamese does not need an infinitive marker like English to in this kind of sentence.

English says:

• try to arrive on time

Vietnamese simply puts the verbs next to each other:

• gắng đến đúng giờ

Here:

• gắng = try
• đến = arrive / come
• đúng giờ = on time

So Vietnamese structure is more like:

• try + arrive + on time

Đến đúng giờ means arrive on time or come at the scheduled time.

Breakdown:

• đến = to come / to arrive
• đúng giờ = on time, at the correct hour/time

So this phrase focuses on the act of arriving at the proper time.

Sometimes yes, depending on context, but the meaning is slightly less specific.

• Gắng đến đúng giờ. = Try to arrive on time.
• Gắng đúng giờ. = sounds incomplete or unnatural.
• Nhớ đúng giờ nhé. = Remember to be on time.
• Đến đúng giờ nhé. = Arrive on time, okay?

So in your sentence, đến is important because it clearly expresses arriving.

It is most naturally understood as a request, reminder, or gentle instruction.

Without extra particles, it can sound fairly direct, but not necessarily rude. The tone depends a lot on context and voice.

If you want it softer or friendlier, you could say:

• Gắng đến đúng giờ nhé.
• Cố gắng đến đúng giờ nhé.

Adding nhé makes it feel warmer and less blunt.

It is understandable, but many speakers would more naturally say:

• Cố gắng đến đúng giờ.
• Ráng đến đúng giờ. (common in southern speech)
• Nhớ đến đúng giờ nhé.
• Đến đúng giờ nhé.

So gắng by itself is possible, but cố gắng is usually the most standard choice for learners.

They are very close in meaning here.

• gắng = try, make an effort
• ráng = try, make an effort

Ráng is especially common in southern Vietnamese and in everyday speech. So you may hear:

• Ráng đến đúng giờ nhé.

This means essentially the same thing as:

• Gắng đến đúng giờ nhé.

For a learner, it is useful to recognize both.

Yes. You can say:

• Hãy cố gắng đến đúng giờ.

Hãy is often used to mark a suggestion, instruction, or exhortation, similar to please / do / should depending on context.

However, in everyday spoken Vietnamese, people often leave hãy out. So:

• Cố gắng đến đúng giờ. sounds natural
• Hãy cố gắng đến đúng giờ. sounds a bit more formal, written, or deliberate

By itself, it is neutral but somewhat direct.

If you are speaking to:

• a friend: it can be fine
• a child: also fine
• a coworker or someone you want to sound gentler with: adding a softening word helps

More polite/friendly versions:

• Cố gắng đến đúng giờ nhé.
• Vui lòng đến đúng giờ. = Please arrive on time.
• Nhớ đến đúng giờ nhé. = Remember to arrive on time, okay?

So politeness in Vietnamese is often adjusted with particles like nhé, or with more formal wording like vui lòng.

They are related, but not identical.

• đúng giờ = on time, at the scheduled time
• đúng lúc = at the right moment, just in time, timely

In this sentence, đúng giờ is the correct choice because it is about arriving at a set time.

Examples:

• Đến đúng giờ. = Arrive on time.
• Anh ấy đến đúng lúc. = He arrived at just the right moment.

So đúng giờ is about schedule; đúng lúc is about timing in a broader sense.