Learn Hardcore Turkish: Kız arkadaşım “beşte gelirim” diye yazdı, saat dilimi farkını da ekledi. - My girlfriend wrote “I’ll come at five” and also added the time zone difference.

Diye introduces the content of speech/thought/writing. Here it means “saying/that,” so the whole chunk means “(she) wrote that ‘I’ll come at five.’” It’s the most natural way to attach a quoted clause to verbs like dedi, yazdı, sordu, düşündü, bağırdı, etc.

Without diye, you’d normally need a different structure: e.g., Beşte geleceğini yazdı (“she wrote that she would come at five,” using a nominalized verb).
You can still use punctuation and no diye (e.g., with a colon), but diye is very idiomatic in everyday Turkish.

Why is it gelirim instead of geleceğim if the meaning is “I’ll come”?

Gelirim is the aorist (“simple present”) form, but in first person it often expresses willingness/promise/quick decision: “I’ll come (sure/okay).” With a time expression like beşte, it naturally reads as a near-future promise.
Geleceğim is the plain future (“I will come”) and can sound more planned, scheduled, or neutral. Both are possible; the nuance of gelirim is a bit more informal and “I’m up for it.”

How does beşte mean “at five”?

It’s the locative case on the number “five”:

beş + -de/-da (locative) → because the final consonant of beş (ş) is voiceless, the suffix becomes -te → beşte = “at five.”
If you write the numeral, it’s 5’te (apostrophe before the suffix).
Other examples: üçte (at three), yedide (at seven), dokuzda (at nine).

Do I need to say saat (as in saat beşte)?

No. Beşte alone already means “at five (o’clock).” Adding saat is optional and can sound a bit more explicit or formal: saat beşte or saat 5’te.

What does da in farkını da mean, and why is it placed there?

This da/de is the additive clitic meaning “also/too.” It attaches to the word it emphasizes and is written separately:

Saat dilimi farkını da ekledi = “(She) also added the time-zone difference.”
Placement matters for nuance: putting da after farkını emphasizes that specific thing as the “also.”

Why is it da (not de) after farkını?

The additive clitic obeys front/back vowel harmony:

Last vowel in farkını is back (ı) → use da.
If the last vowel were a front vowel (e.g., evini), you’d use de: evini de.
Note: Unlike the locative suffix (-de/-da), this clitic never turns into -te/-ta; it’s always spelled separately as de/da.

Why is it farkını and not just farkı or fark?

farkı here is “its difference,” because it’s part of a possessive compound (see next Q&A).
Adding -nı makes it accusative (“the [specific] difference”), since eklemek takes a (usually definite) direct object: fark-ı-nı.
If you said just farkı ekledi, it can be interpreted but sounds incomplete/less natural here; farkını clearly marks a specific, known difference.

What exactly is the structure of saat dilimi farkını?

It’s a chain of noun compounds with possession plus accusative:

saat dilimi = “time zone” (literally “hour slice,” with 3sg possessive on dilim: dilim-i).
saat dilimi farkı = “the difference of the time zone” (head noun fark carries 3sg possessive: fark-ı).
saat dilimi farkını = the same phrase in the accusative (specific direct object): fark-ı-nı.

Could I say zaman farkını instead of saat dilimi farkını?

Yes. Zaman farkı means “time difference” (between two places). Saat dilimi farkı literally “time-zone difference,” is a bit more explicit about zones. Both are common; zaman farkı may be shorter and more colloquial.

Why isn’t it kız arkadaşımın as the subject?

Kız arkadaşım is “my girlfriend” with 1sg possessive -ım, used as the subject: “My girlfriend wrote…”.
Kız arkadaşımın would be genitive and would need a participle (e.g., kız arkadaşımın yazdığı = “what my girlfriend wrote”). You don’t use genitive for a simple subject.

Why is the subject omitted in the second clause (ekledi)?

Turkish is pro-drop: once the subject is clear, you leave it out. The subject of ekledi is still kız arkadaşım from the first clause, so repeating it isn’t needed.

Why yazdı and not dedi?

Yazdı means “(she) wrote,” which fits texting/email. Dedi is “(she) said,” appropriate for spoken quoting. With diye, both work with their respective contexts: … diye yazdı / … diye dedi.

Could I say yazmış instead of yazdı?

You could, but it changes the nuance:

yazdı: simple past—direct, witnessed, factual narration (you saw the message).
yazmış: inferential/reportative—used when you learned it indirectly, or to sound less direct/neutral, sometimes with a slight “apparently” feel.

Is the comma before saat dilimi farkını da ekledi correct? Could I use ve?

Yes, the comma is fine for two closely related clauses with the same subject. You can also say … diye yazdı ve saat dilimi farkını da ekledi. The version without ve is common and natural in Turkish narrative style.

Does gelirim ever mean a habitual “I come (at five)” rather than future?

Yes—outside of a messaging context, the aorist can be habitual/generic: Genelde beşte gelirim = “I usually come at five.” In your sentence, the messaging context plus beşte pushes it toward a promise/plan reading (“I’ll come at five”).

Is beşte the same as saying “by five” or “around five”?

No. Beşte is “at five (exactly).”

“by five” is usually beşe kadar.
“around five” is beş gibi / beş sularında.

Could I swap the order and say Kız arkadaşım saat dilimi farkını da ekleyip beşte gelirim diye yazdı?

Yes. Using -ip links actions (“adding … and then writing …”) and is natural. It slightly foregrounds the adding as a step before/along with writing. Both orders are fine; choose based on what you want to highlight first.

Is the meaning of kız arkadaşım always “girlfriend,” or can it be just a female friend?

Context decides. Kız arkadaş commonly means “girlfriend” (romantic), but it can also mean “female friend.” If ambiguity matters, speakers often clarify with context or use sevgilim for romantic partner and arkadaşım (or specify) for a non-romantic friend.