Comment by js2

There are lots of random web sites claiming how to read the Yuasa date code format, but the only official document I found from Yuasa says "contact us for help decoding the date". Here's a photo of the exact same battery on Amazon with a date code of "291118H0". That must be DDMMYY unless the battery was sent to Amazon from the future (or the photo is forged):

https://www.amazon.co.uk/Yucel-Y1-2-6-Sealed-Rechargeable-Ba...

And I just found this EU Declaration of Conformity which includes the Y1.2-6 and says the date code is DDMMYY:

https://www.farnell.com/datasheets/4633451.pdf