Why does Excel turn 「3月4日」 or a string of digits into a date?

Question

Weirdo · Accepted Answer

It gets stored as a date serial, not the characters you typed. Excel is preprogrammed to treat date-like input as a date: 12/2 becomes 2-Dec; a number with a slash or hyphen, or 「3月4日」 in a Chinese locale, often gets read as a date too. To keep the original string, format the cells as Text first, or prefix the entry with an apostrophe (').

Microsoft is blunt: Excel is preprogrammed to make dates easier to enter — 12/2 becomes 2-Dec. A fraction like 3/4 can turn into 4-Mar; values such as 1/47 or 11-53, with a slash or hyphen, get the same treatment. 「3月4日」 is that kind of date-like input: the cell does not keep the string. Workarounds are to open Format Cells and set the category to Text before you type, or to start the entry with an apostrophe; the apostrophe is not shown after Enter. Both have to happen before the conversion.

Excel stores dates as sequential serial values. In the 1900 date system (the Windows default), 1 January 1900 is serial number 1; switch the cell to General and you see the number. That is why a pile of digits, or a cell that already became a date, can display as some other day: the format is painting a calendar onto a count of days. Excel inherited this serial system from Lotus 1-2-3, including the assumption that 1900 was a leap year (it was not). A 1904 date system also exists; the same calendar day differs by 1,462 serial days between the two.

Why does Excel turn 「3月4日」 or a string of digits into a date?

It reads a date, so the string is gone

A date in the cell is a serial number, not text