Teslim tarihi değiştiğine göre son tarihi takvimime yeniden yazmalıyım.

Teslim tarihi is a very common Turkish noun compound pattern.

• teslim = delivery
• tarih = date
• tarihi = date + compound marker

So teslim tarihi means delivery date.

This is called an indefinite noun compound. In this pattern:

• the first noun usually stays plain: teslim
• the second noun takes a possessive-looking ending: tarih-i

That is why it is teslim tarihi, not usually teslimin tarihi.

Compare:

• okul kapısı = school gate
• yemek masası = dining table
• teslim tarihi = delivery date

Teslimin tarihi is grammatically possible in some contexts, but it sounds more like the date of the delivery in a more specific, analytical way. In ordinary usage, teslim tarihi is the natural form.

No — this is a very important distinction.

In teslim tarihi, the -i is part of a noun compound.

In son tarihi, the -i is the accusative case ending on the direct object.

Breakdown:

• son tarih = final date / deadline
• son tarihi = the final date / the deadline (as a definite object)

So in this sentence:

• teslim tarihi → compound
• son tarihi → accusative-marked object

This is why the two phrases look similar but are built differently.

A quick comparison:

• Teslim tarihi değişti. = The delivery date changed.
• Son tarihi yazmalıyım. = I should write down the deadline.

In the second one, son tarihi is the thing being written, so it takes the definite object ending.

It is built from the verb değişmek = to change.

A simplified breakdown is:

• değiş- = change
• değiştiği = that it changed / its having changed
• değiştiğine = to the fact that it changed
• değiştiğine göre = according to the fact that it changed, which naturally becomes since / given that / if … has changed

So this whole part introduces the reason or basis for the speaker’s conclusion.

You do not need to produce the full internal morphology every time, but it helps to recognize -diğine göre as a very common pattern meaning:

• since
• given that
• judging by the fact that
• if it turns out that

Both can often translate as because / since, but they are not exactly the same.

değiştiğine göre

This often means something like:

• given that it has changed
• since it has changed
• if that’s the case

It sounds like the speaker is drawing a conclusion from a fact.

değiştiği için

This is a more direct because:

• because it changed

So:

• Teslim tarihi değiştiği için... = Because the delivery date changed...
• Teslim tarihi değiştiğine göre... = Since the delivery date has changed / given that the delivery date has changed...

In your sentence, değiştiğine göre works well because the speaker is reasoning:
If the delivery date has changed, then I should rewrite the deadline in my calendar.

Takvimime breaks down like this:

• takvim = calendar
• takvimim = my calendar
• takvimime = to my calendar

So the ending contains:

• -im = my
• -e = dative case (to)

This gives to my calendar.

Turkish often uses the dative after verbs like yazmak when you are writing something into or onto some target place:

• deftere yazmak = to write in the notebook
• listeye yazmak = to write on the list
• takvime yazmak = to write in/on the calendar

So takvimime is exactly what you would expect here.

Because the sentence is focusing on the destination/target of the writing, not the location where the action happens.

• takvimime yazmak = to write it into my calendar
• takvimimde = in my calendar

With yazmak, Turkish commonly uses the dative for the surface/place/target where something gets written:

• tahtaya yazmak = write on the board
• kağıda yazmak = write on the paper
• ajandama yazmak = write in my planner

If you said takvimimde, that would emphasize location, and it would sound less natural in this structure.

Yeniden means again, anew, or once more.

In this sentence, it suggests that the speaker needs to write the date down another time because something changed.

It is similar to tekrar, and in many situations they are interchangeable:

• yeniden yazmak = write again / rewrite
• tekrar yazmak = write again

A small nuance:

• tekrar often just means again
• yeniden can sometimes feel more like afresh / in a renewed way

Here, yeniden works very naturally because the speaker is updating or rewriting an entry.

Yazmalıyım comes from:

• yaz- = write
• -malı / -meli = should / must
• -yım = I am / I should (1st person singular ending here)

So:

• yazmalıyım = I should write / I must write

This suffix expresses necessity or obligation.

Examples:

• Gitmeliyim. = I should go.
• Çalışmalıyım. = I should study.
• Yazmalıyım. = I should write.

In this sentence, it sounds like the speaker has realized what needs to be done.

It can cover both, depending on context.

The Turkish -malı / -meli form often sits somewhere between:

• should
• need to
• must

In everyday use, it often sounds like a personal conclusion or practical necessity:

• I should
• I need to

So here, yazmalıyım is probably best understood as:

• I should write it down again or
• I need to write it down again

It does not necessarily sound as strong as a strict external command, but it clearly expresses necessity.

Because Turkish often leaves subject pronouns out when they are already clear from the verb ending.

Here, yazmalıyım already tells you the subject is I.

• -yım = first person singular

So ben is unnecessary unless the speaker wants emphasis.

Compare:

• Yazmalıyım. = I should write.
• Ben yazmalıyım. = I should write. / I am the one who should write.

Turkish very often drops pronouns when the verb already shows the person.

Turkish word order is flexible, but the neutral/default pattern is usually that the verb comes at the end.

This sentence follows a very natural Turkish structure:

• Teslim tarihi değiştiğine göre = given that the delivery date changed
• son tarihi = the deadline
• takvimime = into my calendar
• yeniden = again
• yazmalıyım = I should write

So the overall flow is:

reason/background + object + destination + adverb + verb

That is very normal in Turkish.

English often prefers:

• Since the delivery date changed, I should write the deadline in my calendar again.

Turkish naturally saves the main verb for the end.

They are close, but not always identical in every context.

• teslim tarihi = delivery/submission date
• son tarih = final date / deadline

In many real-life situations, they may refer to the same date. But the nuance can be slightly different:

• teslim tarihi focuses on the date of delivery/submission
• son tarih focuses on the idea of a final limit or deadline

So the sentence may be using two near-equivalent expressions, or it may be shifting emphasis slightly:

• the delivery date changed
• therefore I should rewrite the deadline/final date in my calendar

That kind of variation is normal and does not sound strange in Turkish.