Μας έστειλαν νέα ημερομηνία, γιατί ο προγραμματισμένος έλεγχος μεταφέρθηκε για τη Δευτέρα.

Here μας means to us: They sent us a new date.

It is a short unstressed pronoun, often called a clitic pronoun. Greek uses these very often with verbs:

• μου έστειλαν = they sent me
• σου έστειλαν = they sent you
• μας έστειλαν = they sent us

The same form μας can also mean our in other contexts, but not in this sentence.

Because short object pronouns in Modern Greek normally go before a finite verb:

• μας έστειλαν
• μου είπε
• τους είδα

So μας έστειλαν is the normal order.
You usually see the pronoun after the verb mainly with positive imperatives, for example:

• στείλτε μας μήνυμα = send us a message

Greek often leaves out subject pronouns when the verb ending already shows who the subject is. This is very normal.

The ending -αν in έστειλαν tells you the subject is they. So Greek does not need to say αυτοί unless it wants emphasis or contrast.

So the sentence naturally means something like:

• They sent us a new date

The actual they could be understood from context: the office, the company, the organizers, the lab, and so on.

Because it is indefinite here: a new date, not the new date.

So:

• νέα ημερομηνία = a new date
• τη νέα ημερομηνία = the new date

Greek often omits the article when it means an indefinite noun, just as English uses a/an.

νέα is an adjective, and it must agree with ημερομηνία in:

• gender
• number
• case

ημερομηνία is feminine singular, and here it is the object of the verb, so it is in the accusative. The adjective matches it:

• νέα ημερομηνία

A detail that often confuses learners: for many feminine nouns in -α, the nominative and accusative singular look the same, so you do not see a visible change here.

προγραμματισμένος means scheduled or planned.

It comes from the verb προγραμματίζω = to schedule / to plan. In this sentence it works like an adjective describing έλεγχος.

Because έλεγχος is masculine singular nominative, the adjective is also masculine singular nominative:

• ο προγραμματισμένος έλεγχος = the scheduled inspection/check

If the noun changed, the adjective would change too:

• η προγραμματισμένη συνάντηση = the scheduled meeting
• το προγραμματισμένο ραντεβού = the scheduled appointment

έλεγχος is a broad word that can mean check, inspection, test, review, or control, depending on context.

In administrative or technical contexts, it often means something like:

• an inspection
• a checkup
• a scheduled check

So in this sentence, ο προγραμματισμένος έλεγχος is the planned or scheduled inspection/check that got moved.

μεταφέρθηκε is the aorist passive of μεταφέρω.

Basic idea:

• μεταφέρω = I move / transfer
• μεταφέρθηκε = it was moved / it got moved

In this sentence, a natural English rendering is:

• was moved
• was rescheduled

This passive form is very common in formal or office-style Greek.

With dates, appointments, and scheduled events, για + article + time expression often means the new planned time.

So:

• μεταφέρθηκε για τη Δευτέρα = it was moved to Monday

This is a very useful pattern with rescheduling language.

A helpful contrast:

• μεταφέρθηκε για τη Δευτέρα = it was moved to Monday
• μεταφέρθηκε τη Δευτέρα = it was moved on Monday

So the για is important.

Greek normally uses the definite article with days of the week.

So:

• τη Δευτέρα = on Monday
• την Τρίτη = on Tuesday
• την Παρασκευή = on Friday

This is just normal Greek usage. English says on Monday without an article, but Greek usually says the Monday structurally.

So για τη Δευτέρα is the regular Greek way to say for Monday / to Monday in this context.

Because the final -ν of την is often dropped before many consonants in Modern Greek.

So both spellings may be seen, but τη Δευτέρα is very common and completely normal.

As a general rule, the final -ν is more likely to stay before vowels and certain consonants, but before Δ it is often omitted:

• τη Δευτέρα

This is one of those small spelling-and-pronunciation habits that becomes natural with exposure.

Here it means because.

Greek γιατί can mean either:

• why
• because

You tell from context.

Examples:

• Γιατί έφυγες; = Why did you leave?
• Έφυγα γιατί νύσταζα. = I left because I was sleepy.

In your sentence, it introduces the reason:

• they sent a new date because the scheduled inspection was moved

Because the sentence is talking about two completed past events:

• they sent a new date
• the inspection was moved

The Greek aorist is the normal tense for this kind of simple past narration.

So:

• έστειλαν = they sent
• μεταφέρθηκε = it was moved

If the speaker wanted to describe an ongoing, repeated, or background past action, Greek would more likely use the imperfect instead. Here the aorist is the natural choice.