Learn Hardcore Japanese: kodomo no koro ha mainiti sakkaa wo simasita. - When I was a child, I played soccer every day.

子供のころは …
- は marks topic/contrast: “As for when I was a child, I played soccer every day.”
- It frames “my childhood” as the general topic you’re talking about.
子供のころに …
- に marks the time when something happens: “During my childhood, I played soccer every day.”
- Feels a bit more like a straightforward time marker, less like a contrast.

In this sentence, using は is very natural because you’re making a general statement about that period of life.

Why doesn’t 毎日 have a particle like に? Could I say 毎日にサッカーをしました?

Time expressions like 毎日 (every day) usually appear without a particle when they simply answer “when?”:

毎日サッカーをしました。 – I played soccer every day.
明日行きます。 – I’ll go tomorrow.
来週会います。 – I’ll meet (you) next week.

毎日にサッカーをしました is unnatural; you normally don’t add に after 毎日, 毎朝, 毎晩, etc.

You can add は for emphasis/contrast:

毎日はサッカーをしました。 – I played soccer every day (as opposed to some other frequency).

Why is there no word for “I” in the sentence? How do we know it means “When I was a child”?

Japanese often drops the subject when it’s clear from context.

In a normal conversation, if you say:

子供のころは毎日サッカーをしました。

people will naturally understand it as:

“When I was a child, I played soccer every day.”

If you wanted to specify someone else, you’d usually add that person explicitly:

私は子供のころ毎日サッカーをしました。 – I, when I was a child, …
兄は子供のころ毎日サッカーをしました。 – My older brother, when he was a child, …

So “I” is implied rather than spoken.

Why is サッカー followed by を? In English we say “play soccer,” not “do soccer.”

In Japanese, the natural expression is サッカーをする, literally “to do soccer.”
Here, サッカー is treated as the direct object of the verb する (“to do”), so it takes を:

サッカーをする – to play soccer
サッカーをしました – played soccer

This noun + を + する pattern is extremely common:

勉強をする – to study
宿題をする – to do homework
練習をする – to practice

So サッカーをしました is just the polite past form of サッカーをする.

Does 子供のころは毎日サッカーをしました really mean “I used to play soccer every day”? Is しました okay for a repeated/habitual action?

Yes. しました (past tense of する) can describe repeated or habitual actions in the past, not just one-time actions.

So 子供のころは毎日サッカーをしました naturally means:

“When I was a child, I used to play soccer every day.”

Another common way is using 〜ていました, which more strongly highlights the ongoing habit:

子供のころは毎日サッカーをしていました。

Nuance:

しました – neutral past, still fine for a habit (especially with 毎日, いつも, etc.).
していました – makes the “continuous/habitual” flavor a bit stronger.

Could I drop は and say 子供のころ毎日サッカーをしました? What’s the difference?

Yes, you can say:

子供のころ毎日サッカーをしました。

It’s grammatically fine and natural.

Differences:

子供のころは毎日サッカーをしました。
- 子供のころ is the topic.
- Slightly stronger feeling of “as for my childhood…”
子供のころ毎日サッカーをしました。
- 子供のころ behaves more like a simple time phrase (“when I was a child”).
- A bit more neutral in tone.

In many everyday contexts, both sound okay, with only a subtle difference in emphasis.

Can 子供のころは毎日サッカーをしました ever mean “The children played soccer every day,” not “I”?

By itself, it most naturally means “When I was a child, I played soccer every day.”

Japanese doesn’t mark singular/plural the way English does, and the subject is omitted, so in theory it could refer to someone else, but then context or extra words usually clarify it:

彼は子供のころ毎日サッカーをしました。 – He, when he was a child, played soccer every day.
子供たちは毎日サッカーをしました。 – The children played soccer every day.

Your original sentence does not mean “the children (as a group) when they were children.” It is understood as “(I) when I was a child…,” unless something before/after the sentence clearly sets a different subject.

Can I change the word order, like 毎日子供のころはサッカーをしました or 子供のころはサッカーを毎日しました?

Word order in Japanese is somewhat flexible, but not everything sounds natural.

子供のころは毎日サッカーをしました。 – very natural (original).
子供のころ毎日サッカーをしました。 – also natural (dropped は).
子供のころはサッカーを毎日しました。 – okay; slightly stronger emphasis on 毎日.

Sounds odd:

毎日子供のころはサッカーをしました。
This is awkward because 毎日 (“every day”) doesn’t pair well with 子供のころは right after it; it’s like “Every day, as for when I was a child…” which is logically weird.

A safe rule: put the bigger time frame (子供のころ) earlier, and the repeated time word (毎日) closer to the verb.

Why is 子供 in kanji but ころ in hiragana? Can I write 子どもの頃 or 子供の頃 instead?

Yes, several spellings are used in real Japanese:

子供のころ
子どものころ
子供の頃
子どもの頃

All are readable. Some notes:

子供 / 子ども: both are common. Many publications prefer 子ども (hiragana for ども) for stylistic or guideline reasons, but 子供 is also standard.
ころ / 頃:
- ころ (hiragana) is common in everyday writing and textbooks.
- 頃 (kanji) looks a bit more formal or literary.

So 子供のころ in your sentence is a perfectly normal beginner-friendly spelling.

What’s the difference between ころ and ごろ, and why is it ころ here, not ごろ?

Both ころ and ごろ relate to “around (a time),” but they’re used a bit differently.

Rough guideline:

ころ – often used for periods/stages, especially with life stages or clauses:
- 子供のころ – when I was a child / in my childhood
- 学生のころ – when I was a student
- 日本にいたころ – when I was in Japan
ごろ – more often used for approximate clock times or specific dates:
- 3時ごろ – around 3 o’clock
- 1990年ごろ – around 1990
- 夏ごろ – around summer

For childhood as a life stage, the usual expression is 子供のころ (or 子供の頃), not 子供のごろ.

What politeness level is しました, and when would I use した instead?

しました is the polite past form of する.
- Used in normal polite speech (the です／ます style): with teachers, in most workplaces, with people you’re not very close to, etc.
した is the plain past form.
- Used with friends, family, in casual writing, diaries, etc.

So:

Polite:
- 子供のころは毎日サッカーをしました。
Casual/plain:
- 子供のころは毎日サッカーをした。
- Very casual speech may even shorten to 子供のころは毎日サッカーしてた。 (spoken form of していた)

The meaning is the same; only the formality level changes.