Japanese writing order for the dates and details will be as below;
YEAR / ANNÉE
MONTHS / MOIS
DATES / JOURS
Below dates are special ones. Everything except on the picture below goes with にち (NICHI).
Day of the Week is in another article. Please go check the link below. ↓
For xx months
We use “ヶ月(かげつ・kagétsu)” for “month”. The Kanji for かげつ can be ヶ月, ヵ月, カ月 or even か月. Everything is used very often. The kanji, 間（かん・kan）, which means during or for (in French, pendant, pour), is optional.
For xx days
We use the same ones with calendar dates except for 1 day.
From 2 days, the kanji, 間（かん・kan）, which means during or for (in French, pendant, pour), is optional.
How do we recognize if it is a date of duration of days?
The key is a particle. If you are talking about A Specific Time (date, o’clock, etc.) you need to add に after the counter.
If you are talking about duration of time (for 3 days, for 5 months, for 4 hours. etc.) we add no particle after the counter. If you would like, you can add 間（かん・kan）, which means during or for (in French, pendant, pour), however it is not necessary.
- On (June) 8th, I got vaccinated. ＝６月８日に 、ワクチンを打ちました。
- I ate pizza for 3 days. = ３日（間）、ピザを食べました。