Celengan itu saya buka pada akhir bulan untuk menghitung tabungan tambahan.

Celengan means a money box, coin bank, or piggy bank. In modern Indonesian, it does not have to be pig-shaped. It can be any container used to save small amounts of money.

So in this sentence, celengan itu simply means that/the money box.

Itu is a demonstrative word meaning that. After a noun, it can also function a lot like the, especially when referring to something already known in the conversation.

So:

• celengan = a money box / piggy bank
• celengan itu = that money box / the money box

In Indonesian, demonstratives usually come after the noun, not before it.

Indonesian often puts the thing being talked about first for emphasis or topic marking.

So:

• Saya membuka celengan itu = I open that money box
• Celengan itu saya buka = That money box, I open / I open that money box

The second version highlights celengan itu. It sounds natural in Indonesian when the speaker wants to focus on the object first.

It is commonly described as a passive-like construction, often called passive type 2 in Indonesian grammar.

In this pattern:

• the thing affected comes first: celengan itu
• the agent is a pronoun: saya
• the verb usually appears without meN-: buka, not membuka

So Celengan itu saya buka is structurally different from the straightforward active sentence Saya membuka celengan itu.

In natural English, both may translate similarly, but the Indonesian structure gives more prominence to celengan itu.

Because in this kind of pronoun-agent construction, the verb is usually a bare base form.

So:

• Saya membuka celengan itu = regular active
• Celengan itu saya buka = object-first, passive-like structure

Using membuka after saya in this exact pattern would sound less natural.

A very useful comparison:

• Buku itu saya baca
• Suratnya saya kirim
• Celengan itu saya buka

This pattern is very common in Indonesian.

Pada akhir bulan means at the end of the month.

Pada is often used with time expressions, especially in slightly more formal or careful Indonesian.

So:

• pada akhir bulan = at the end of the month
• di akhir bulan = also common, a little more everyday in many contexts

Both can be natural, but pada often sounds a bit more formal or standard when talking about time.

By itself, it can be understood either way depending on context.

This sentence could mean:

• a habitual action: I open it at the end of each month
• a specific occasion: I open it at the end of the month

Indonesian often leaves this kind of distinction to context rather than marking it clearly in the verb.

If the speaker wanted to be more explicit about repetition, they could say something like setiap akhir bulan = every end of the month / at the end of every month.

Untuk introduces a purpose.

So:

• untuk menghitung tabungan tambahan = to count the extra savings / in order to calculate the additional savings

It tells you why the speaker opens the money box.

A simple way to read the structure is:

• Celengan itu saya buka = I open that money box
• pada akhir bulan = at the end of the month
• untuk menghitung tabungan tambahan = to count the additional savings

Menghitung is the standard meN- verb form meaning to count or to calculate.

After untuk, Indonesian often uses a verb like this to express purpose:

• untuk menghitung = to count
• untuk melihat = to see
• untuk membeli = to buy

In casual speech, Indonesians sometimes shorten forms, but untuk menghitung is the standard and most neutral version here.

Tabungan means savings.
Tambahan means additional, extra, or added.

So tabungan tambahan means:

• additional savings
• extra savings
• possibly the extra amount that has been saved

The exact nuance depends on context, but the basic idea is money saved in addition to the main savings amount.

Because Indonesian usually places modifiers after the noun they describe.

So:

• tabungan tambahan = additional savings
• rumah besar = big house
• buku baru = new book

This noun + modifier order is very common in Indonesian.

Indonesian verbs usually do not change form for tense the way English verbs do.

So buka can mean:

• open
• opened
• will open

The time is understood from context or from time words such as pada akhir bulan.

If needed, Indonesian can add words like:

• sudah = already
• sedang = in progress
• akan = will

For example:

• Celengan itu sudah saya buka = I have already opened that money box
• Celengan itu akan saya buka = I will open that money box

In the original sentence, the exact tense or aspect comes from context rather than verb endings.