> Can a birthday be change by doing a deed poll.
No. You cannot change your date of birth by any means.
If your date of birth was incorrectly-recorded on your birth certificate (this can sometimes happen when a birth happens late at night but isn’t registered until the following morning, for example), then this can be corrected, but it’s rarely an easy process. You need to be able to prove that the information is incorrect, and what the correct information is (e.g. via an affidavit from the registering doctor) either to the local register office in which the birth was registered, or to the General Register Office. Either way, full details can be found at https://www.gov.uk/correct-birth-registration
If you simply want to “change” your date of birth like you might change your name – this simply isn’t permitted. Otherwise I could declare myself to be elderly and retire tomorrow (and children would declare themselves to be adults to get into bars!).