I had pretty much the same with my birthday being in October, some of us are just unlucky.
My daughter was born on the 5th of April back in the eighties and you used get child tax allowance back then and it would have been backdated to the start of the tax year, so would have had a full years tax rebate with the new tax year starting on the 6th but they stopped doing the child tax allowance that year and put it on the family allowance.
Same again with my wife who’s been playing catch up with the retirement age that seem to have another year added on just as she reach the retirement age.