Hi Chantel,
Thanks for using Microsoft products and posting in the community, I'm glad to offer help.
According to your description, you can follow the steps below to format the 'Age' column:
- Create a 'Date and time' column named 'Date of Birth'
- Create a 'Calculated' column named Age and enter the formula as shown below (Note: to create a 'Calculated' column, please click '+Add column' > More…)
- Select the 'Age' column > Column settings… > Format this column > Advanced mode > copy and paste the following code:
{
"$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
"elmType": "div",
"txtContent": "=substring(toString(Number(@now-@currentField)/86400000/365),0,indexOf(toString(Number(@now-@currentField)/86400000/365),'.'))"
}
Reference: Create an 'Age/Days old' column in SharePoint List - Microsoft Tech Community
Hope the above suggestion can be helpful, and please feel free to let me know if it works, I'll continue to help you.
Best Regards,
Arck