Here, 今日 is read きょう, meaning today.
A native English speaker may notice that 今日 can sometimes be read differently, especially in set expressions, but in an everyday sentence like this, きょう is the normal reading.
Japanese uses the past form here because the action is viewed as completed.
So 今日入社しました means that the speaker joined the company today, and that joining has already happened.
This is similar to English:
Even though today includes the present day, the act of joining is treated as a completed event, so the past tense is natural.
Because Japanese often leaves out information that is clear from context.
So 今日入社しました。 naturally implies something like:
But Japanese does not need to say 私は unless there is a reason to emphasize or contrast the subject.
For example:
This is grammatical, but in many real situations, 私は is unnecessary.
Both can relate to joining a company, but they are not exactly the same.
入社する is a more specific and standard word for joining a company as an employee. It is common in business settings.
会社に入る is more general. It can also mean joining a company, but 入社する sounds more formal and more precise in workplace contexts.
So in a business situation, 入社しました is often the more natural choice.
入社 means joining the company as an employee.
It does not usually mean simply physically entering the office building. For that, Japanese would use a different expression, such as one meaning go into the building or enter the office.
Depending on context, 入社しました can suggest:
So it is about employment status, not just movement into a place.
Because the verb ends in ました, which is the polite past ending.
The polite form is common when:
Since 入社 is already a business-related word, the polite form fits very naturally here.
Yes, absolutely.
It would sound natural in a business or workplace context, especially if someone is introducing themselves as a new employee.
For example:
Or more naturally with a pause:
So the sentence works well as part of a formal introduction.
The most natural order is:
Japanese word order is more flexible than English, but time expressions like 今日 often come near the beginning.
You could also say:
but that would sound unusual in normal speech unless you are adding emphasis or speaking dramatically.
So for a learner, 今日入社しました。 is the safest and most natural pattern.
You would normally add the company before 入社しました.
For example:
Here, に marks the company you joined.
So:
Without a company name, the sentence still sounds natural if the company is already understood from context.
In speech, there often is a slight pause:
In writing, a comma is optional. Japanese often omits commas in short simple sentences, so both are fine:
The comma can make the sentence slightly easier to read, but it is not required.