You need to provide your date of birth (and your partner's date of birth if you have a couples membership) so that we can ensure that you have the correct membership package.
Some of the membership packages are only available to certain age groups, for example, YBN (youth) or packages for those over 80.
The system attempts to calculate which packages are appropriate for your age so when you sign up or renew the process is simplified because you only have to select between 2 or 3 relevant subscriptions rather than the full range.
At renewal time the system attempts to automatically move you onto the correct package - which is almost always cheaper than your current package. For example, a person on the "Individual under 65" package would automatically be moved on to the "individual aged 65 to 79" package at their 65th birthday. At the time of writing that would represent a saving of £2 per annum. (Similarly, the move from the "65 to 79" package to the "over 80" package would represent a saving of £6 per annum.)