It doesn't really solve your problem, TOGAR, but maybe you could just get little file cards and write the date on them and flash it front of the camera at the beginning of a flying day.
Not trying to be snarky or anything, just offering a solution. Hopefully, it is cheap and easy enough for you.
BTW, I know what you mean about the poor English of the guys who write the manuals. I have a Thunder charger with the ability store different programs in it and I have yet to figure out how to do it. The manual is pretty much no help. And I'm an equipment engineer who has figured out temperature controllers, industrial servos, plc's and a lot of other menu-driven devices but can't seem to crack the code on this charger. I'm not giving up though!