I will move to Japan on April 15th because of work for 2 years. I heard that in Japan, the income tax occurs for the period of service for the resident. In my case, when is the start occurring the tax as resident? And when I come back to my country after 2 years, when is the start becoming non-resident?
The day you become resident or Non-resident is calculated based on the tax laws that “the first day of period is not included”.
Therefore, for the question, the next day of the 15th April (=16th April) will be the start of your income to be taxable.
And in the case you will return to your country after 2 years, you will become a non-resident the next day after your return.