is a combination of two different types of particles. The 副助詞（ふくじょし） (adverbial particle) まで
, and the 格助詞（かくじょし） (case-marking particle) に
is verb similar to まで
when it means ‘until’. However, there is one very important distinction. This distinction is that までに
means ‘by’, not ‘until’.
To use までに
, we will need to attach it to the end of a noun, or verb in the non-past form.
Please come to the station by 5 o’clock.
Please tidy up by the time you go out to play.
To understand the difference between まで
, and までに
, we need to remember that に
usually marks a ‘target’, or a ‘destination’ for where something will happen. In this case, まで
is the ‘target’ that に
is marking. This is due to the fact that まで
means 'as far as' (まで
is sometimes written using kanji 迄（まで）
, especially in older/formal texts, and newspapers).
I will write a report by next month. (Focus is on ‘next month’ being the deadline)
I am writing a report until next month. (Focus is on ‘next month’ being the end point for something that will continue until that point)
In this way, までに
more literally means ‘(A) as far as (に
marks the target), (B).
meant ‘as far as’ in regard to the passing of a particular event. However, in modern Japanese, most people will assume that the speaker means ‘by the beginning of (A)’. Due to this, sentences that have a very broad event, such as 夏（なつ）までに
could actually be interpreted as ‘by the start of summer’, or ‘before the end of summer’, depending on who you are talking to. In these cases, it would be better to add a more specific time frame.