It looks oddly because the month and year are not fully visible:
See also:
- How to show the «Date of Birth» calendar on the frontend «Create New Customer Account» and «Edit Account Information» pages?
- The «Date of Birth» calendar icon is wrongly wrapped to the next line on the frontend «Edit Account Information» page
- How is the «Date of Birth» calendar implemented on the frontend «Edit Account Information» page?
- How to add a date picker to the frontend?