Mayıs planı netleşince takvime yeni bir not düştüm.

Because Mayıs planı is a Turkish noun compound, meaning something like May plan or the plan for May.

In this kind of structure:

• the first noun modifies the second noun
• the second noun usually takes the 3rd person possessive suffix
• here that suffix is -ı

So:

• Mayıs = May
• planı = its plan / plan of it

Together, Mayıs planı means the May plan or the plan for May.

This -ı is not the accusative here. It is part of the noun-compound structure.

Mayıs planı and Mayıs’ın planı are related, but they are not used in exactly the same way.

• Mayıs planı = May plan / plan for May
  This is the more compact noun-compound form.
• Mayıs’ın planı = May’s plan / the plan of May
  This sounds more like a full possessive relationship.

In many everyday contexts, Turkish prefers the shorter compound form when one noun is simply classifying another. So Mayıs planı is very natural for the May plan.

Netleşince comes from:

• net = clear
• netleşmek = to become clear, to be finalized
• -ince / -ınca = when, once, after

So:

• netleşince = when it became clear
• or once it was finalized

This -ince form is a very common way to say when X happened or once X happened.

For example:

• Eve gelince beni ara. = Call me when you get home.
• İşi bitirince çıkacağım. = I’ll leave once I finish the work.

They are very close, and in many situations both can be translated as when.

But there is often a slight difference in feel:

• netleşince often sounds more like once it became clear / as soon as it became clear
• netleştiğinde can sound a bit more neutral or formal: when it had become clear

In this sentence, netleşince sounds very natural because it suggests a sequence:

1. the May plan became clear
2. then I added a note to the calendar

Takvime is takvim + -e, the dative case.

• takvim = calendar
• takvime = to the calendar

The dative often corresponds to to, toward, or sometimes onto, depending on the verb.

Here, takvime not düşmek means something like:

• to add a note to the calendar
• to jot something down on the calendar

So takvime is used because the note is being entered/added to the calendar.

Good question. Literally, takvimde means in/on the calendar, while takvime means to the calendar.

But with the expression not düşmek, Turkish commonly uses the dative:

• takvime not düşmek = to make/add a note to the calendar

So this is not just about physical location. It is about adding something into the calendar record.

If you used takvimde, it would focus more on where the note is located, not on the act of entering it.

Yes, the basic meaning of düşmek is to fall. But in Turkish, it also appears in several idiomatic expressions.

Here, not düşmek means:

• to make a note
• to jot down a note
• to add a note

So takvime yeni bir not düştüm means:

• I added a new note to the calendar
• I jotted a new note into the calendar

This is a good example of a verb having an idiomatic meaning in a fixed expression.

Bir here means a.

So:

• yeni bir not = a new note

Using bir makes the noun clearly singular and indefinite, which is very natural in this sentence.

Without bir, yeni not might still be understandable in some contexts, but yeni bir not sounds more complete and standard for a new note.

Because not is an indefinite direct object here.

In Turkish:

• an indefinite direct object usually has no accusative ending
• a definite/specific direct object usually takes the accusative

So:

• yeni bir not düştüm = I added a new note
  (some new note, not previously identified)
• notu düştüm would suggest the note
  (a specific note already known in the conversation)

Since the sentence introduces the note as new information, the bare form not is correct.

Düştüm is in the simple past tense.

It is formed from:

• düş- = verb stem
• -tü / -tı / -du / -dü = past tense suffix
• -m = I

Because of sound changes and vowel harmony, it appears here as düştüm.

So it means:

• I fell in the basic literal sense
• but here, in the idiom not düşmek, it means I made/jotted/added a note

Turkish word order is often more flexible than English, but the default pattern is that the verb comes at the end.

This sentence is structured like:

• Mayıs planı netleşince = when the May plan became clear
• takvime yeni bir not = a new note to the calendar
• düştüm = I added/jotted

So the whole sentence naturally builds toward the final verb.

A rough structure is:

[time/condition clause] + [other sentence elements] + [main verb]

That is very typical Turkish sentence order.

The subject is Mayıs planı.

So:

• Mayıs planı netleşince = when the May plan became clear/finalized

In Turkish, subordinate verb forms like -ince do not need a separate subject marker if the subject is already expressed in the clause.

Yes, very strongly.

The sentence suggests this sequence:

1. Mayıs planı netleşti = the May plan became clear/finalized
2. takvime yeni bir not düştüm = I added a new note to the calendar

So -ince often gives the sense of once that happened, then this happened.

That sequencing is an important part of why netleşince sounds natural here.