To start this lesson out, I always bring in my old American calendars (Goats in Trees, the kids love it and so do I). If you don't have any calendars from your country you can skip this, but if you have some, it's good to get the kids to look at them and compare some differences. I always point out that mine has three languages (English, Spanish, French), while Japan's only has one. There's no blue and red used for days on the American ones. The American ones always show the moon phases (though this is becoming more common in Japan, too), etc. etc. I use my name in the PowerPoint here, too, so be sure to change that.
Next, introduce all the months and have the kids repeat for practice. The second time you go through them all, the kids should stand up while saying the month if its their birthday month.
After the months, introduce the ordinal numbers. It's not really important that the kids remember all of these for this lesson. Just the number they need for their own birthday is fine, but they should eventually learn all of them, so I've highlighted the many exceptions in red for these. Again, first time through, just listen and repeat. Second time through, stand while saying it if it's their birthday month.
Then, on to the main activity: a variation of the "Find Someone Who" game in the shape of a bingo board. I like doing "Find Someone Who" this way because regular bingo makes me want to set myself on fire I hate it so much, and having incremental goals during "Find Someone Who" keeps the kids engaged longer. Show the kids the instructions in the PowerPoint (provided in Japanese so everyone is crystal clear). First, they should write their own birthday on the first page in the space provided and make sure they know how to say it. Give them a bit of time to write it, and ask them to raise their hands if they want you to pronounce it before moving on to the game.
When you start the activity, students stand up, walk around the classroom with their bingo sheet, and find a partner. Then they do rock, paper, scissors to determine their conversation roles. The person who wins should ask, "When is your birthday?" The loser responds with their birthday. Then, they switch and the loser asks the winner. When both people have asked the question, they go to their bingo sheets, and choose ONE of the three possible places to write the person's name. For example, "August 27th" can be "born in August" (８月生まれ) or "starts with 2" (２から始まる) or "ends with 7" (７で終わる). They must choose only one of the three, and NOT write the person's name in all three blanks (otherwise the game will be over very quickly). Once they've written the person's name somewhere, they say goodbye and find a new partner. They can't ask the same person more than once (unless they talk to everyone in the class, then they can start asking the same people again). Once they get a bingo, they should come to you and get a sticker (or stamp or whatever reward you want to give). For this activity, since it's a little hard to find people with specific birthdays, I give them one sticker per bingo they get. But if you think this is too many stickers, you can change it so that the second sticker requires a blackout instead. I set the time limit at 15 minutes for them to try to get as many stickers as they can.
I've included a lesson plan written in English and Japanese, so your Japanese homeroom teachers can read it and know exactly what the plan is.
The font used in this is UDデジタル教科書. It should be on all of your school computers, but I don't have it on my personal computer at home. I prefer it because it has the handwritten lowercase "a" as well as other handwriting differences, but doesn't look like garbage like Comic Sans. If you don't have it, there might be some formatting discrepancies.