Learn Hardcore Greek: Έχω προθεσμία μέχρι την ημερομηνία δεκαπέντε Μαρτίου και τη σημειώνω στο τετράδιό μου, έχω περίπου δύο εβδομάδες ακόμα. - I have a deadline until the date March fifteenth and I note it in my notebook; I still have about two weeks.

προθεσμία sounds a bit more formal/neutral (often used in official contexts).
διορία can sound slightly more colloquial or urgent, but in everyday speech they are often interchangeable.

Why does the sentence say Έχω προθεσμία μέχρι... and not something like Η προθεσμία είναι μέχρι...?

Both are possible:

Έχω προθεσμία μέχρι...
Literally: I have a deadline until...
This focuses on you having a certain amount of time.
Η προθεσμία είναι μέχρι...
The deadline is until...
This focuses on the deadline itself as an impersonal fact.

In everyday Greek, Έχω προθεσμία μέχρι... is very natural and common when you talk about your own time limit. Using είναι would also be correct, just slightly more impersonal.

How should I understand μέχρι την ημερομηνία δεκαπέντε Μαρτίου word by word?

Breakdown:

μέχρι – until / up to
την – feminine accusative singular definite article the
ημερομηνία – date
δεκαπέντε Μαρτίου – 15 March (literally fifteen of March)

So literally:

μέχρι την ημερομηνία δεκαπέντε Μαρτίου
→ until the date (of) 15 March.

It’s a bit wordy; more natural everyday variants would be:

μέχρι τις 15 Μαρτίου
μέχρι 15 Μαρτίου

But the original is grammatically correct and a bit more explicit/formal (“until the date of March 15th”).

Why is Μαρτίου in that form, and not something like Μάρτιος?

Μάρτιος is the nominative form (March as a subject).

In δεκαπέντε Μαρτίου, Μαρτίου is in the genitive case, which in this context means “of March”.

So:

δεκαπέντε Μαρτίου = fifteen (of) March
(exactly like many European languages: Spanish 15 de marzo, Italian 15 marzo with implied di.)

This is the normal way to write dates in Greek:
[day in cardinal number] + [month in genitive]
e.g. τριάντα Ιουνίου – 30 June.

Why is it δεκαπέντε Μαρτίου (15 March) and not an ordinal like δεκάτη πέμπτη Μαρτίου (15th of March)?

Modern Greek usually uses cardinal numbers for dates, not ordinals:

15 Μαρτίου / δεκαπέντε Μαρτίου – standard
δεκάτη πέμπτη Μαρτίου – more formal, old-fashioned, or written in legal/ceremonial contexts.

So in everyday Greek:

μέχρι 15 Μαρτίου is what you’ll hear most.
Using the ordinal (δεκάτη πέμπτη) sounds formal or bureaucratic.

Could I drop την ημερομηνία and just say Έχω προθεσμία μέχρι δεκαπέντε Μαρτίου?

Yes, and that would usually sound more natural:

Έχω προθεσμία μέχρι δεκαπέντε Μαρτίου.
Έχω προθεσμία μέχρι τις 15 Μαρτίου.

Adding την ημερομηνία (the date) is redundant in most everyday situations. It only makes sense if you want to emphasize “this particular date” in a very explicit or formal way, e.g. in official documents: μέχρι την ημερομηνία 15 Μαρτίου 2026.

In και τη σημειώνω στο τετράδιό μου, what does τη refer to, and why is it feminine?

Τη is the feminine accusative singular object pronoun = her/it.

Here it refers back to την ημερομηνία (the date), which is:

feminine (η ημερομηνία),
singular,
and is the direct object of σημειώνω.

So:

και τη σημειώνω στο τετράδιό μου
→ and I note it down in my notebook
where “it” = the date.

You could also say the full noun again:

και σημειώνω την ημερομηνία στο τετράδιό μου – also correct, just more repetitive.

Why is it spelled τη σημειώνω and not την σημειώνω?

The object pronoun την and the article την (feminine accusative singular) often lose the final -ν in front of certain consonants.

Rule of thumb in modern Greek spelling:

την → τη before most consonants (like σ, μ, π, etc.).
την keeps the ν before vowels and some consonants (κ, π, τ, ξ, ψ, γκ, μπ, ντ, τσ, τζ).

Here the next word is σημειώνω (starting with σ), so we normally write:

τη σημειώνω (pronounced ti simeóno).

Both τη and την would be understood, but τη is the standard spelling in this context.

What is the nuance of σημειώνω compared to just γράφω?

Both involve writing, but they’re different:

γράφω – I write (in general: letters, texts, essays, etc.)
σημειώνω – I jot down / I note / I make a note of

In τη σημειώνω στο τετράδιό μου:

The idea is that you quickly record the date as a reminder, not that you write a long text about it.
A very natural translation:
“and I write it down in my notebook” or “and I note it in my notebook.”

Why does τετράδιό μου have the accent on the last syllable, not on -τρά- as in τετράδιο?

Normally, the word is:

τετράδιο – notebook (stress on -τρά-: τετράδιο)

When you add the enclitic pronoun μου (my), Greek spelling rules say:

If a word is stressed on the antepenultimate syllable (like τε-ΤΡΑ-δι-ο)
and you add a clitic (like μου),
you add a second accent on the last syllable of the word.

So it becomes:

το τετράδιό μου – with an extra written accent on -διό.

Pronunciation doesn’t change much; it just shows that the phrase is treated as one phonological unit.

What does στο τετράδιό μου literally mean?

στο is a contraction of:

σε (in / at / on)
το (the, neuter accusative singular)

So:

στο τετράδιό μου = σε το τετράδιό μου → in my notebook.

Word by word:

στο – in/on the
τετράδιό – notebook (with extra accent because of μου)
μου – my

So the phrase literally is in the notebook of mine → in my notebook.

In έχω περίπου δύο εβδομάδες ακόμα, where does περίπου usually go, and could I say this another way?

Περίπου means about / approximately and usually goes before the quantity:

έχω περίπου δύο εβδομάδες ακόμα – I have about two weeks left.

Other natural options:

έχω καμιά δυο εβδομάδες ακόμα (more colloquial: “around two weeks or so”)
μου μένουν περίπου δύο εβδομάδες ακόμα – I have about two weeks left / about two weeks remain for me.

The position of περίπου is normally:

before the number: περίπου δύο εβδομάδες
or, less often, after: δύο εβδομάδες περίπου (also correct).

What’s the difference between ακόμα and ακόμη?

In modern everyday Greek, ακόμα and ακόμη are practically interchangeable and both mean:

still or yet
(time) left / remaining when used like in your sentence.

In έχω περίπου δύο εβδομάδες ακόμα:

It means I still have about two weeks / I have about two weeks left.

Some people feel ακόμη is slightly more formal or literary, but in speech most Greeks freely use both:

έχω ακόμα δουλειά / έχω ακόμη δουλειά – I still have work to do.

Is it OK in Greek to join ...στο τετράδιό μου, έχω περίπου δύο εβδομάδες ακόμα with just a comma?

Yes; Greek is more tolerant of what would be called a comma splice in English.

...και τη σημειώνω στο τετράδιό μου, έχω περίπου δύο εβδομάδες ακόμα.

This is acceptable in Greek, especially in informal writing. You could also write:

...και τη σημειώνω στο τετράδιό μου· έχω περίπου δύο εβδομάδες ακόμα.
(semicolon · in Greek punctuation, used like a “strong comma”)
...και τη σημειώνω στο τετράδιό μου και έχω περίπου δύο εβδομάδες ακόμα.

All are fine; the original with a comma is stylistically natural in Greek but would be considered incorrect punctuation in formal English.