How can I modify customer account attributes in a store?

Hi,

I am a developer for a store, and I was wondering if there is a way to modify the attributes of a customer account. Specifically, during account creation, I want customers to have the choice to optionally input the month and day of their birth. Additionally, I was wondering if there was any way to check how many days an account has existed using Liquid. I want to implement special messages to be sent on the anniversary of the account creation as well as the customer’s birthday (if they chose to disclose the information), and I was having trouble finding any way to implement this.

So far, in customer/register.liquid, I have this for finding the date of birth:

{{ ‘customer.register.date_of_birth’ | t }}

The main issues are:

  1. When the code is ran, there is no label title for the date selector, so it is unclear what the query is asking
  2. The date selector that is built into Shopify asks for month/day/year when I only want to ask and store the information for month/day
  3. This currently stores the information as a note, and I could not find any documentation in Liquid that allows me to interpret customer notes within the code, so the data is essentially useless
    Below, I have included what the account creation menu looks like, as well as what the Date of Birth information looks like in the customer account details

If any of you have a solution to any or all of my issues, your help would be greatly appreciated!