Sharepoint Birthday List

Create Collums:

• Username                           > People or Group
• Birthday                              >  Date Only format
• Next Birthday                      > Calculated field        
• Days until B'day                  > Calculated field

Next Birthday contains following formula:

=DATE(YEAR(Birthday)+DATEDIF(Birthday,TODAY(),"Y"),MONTH(Birthday),DAY(Birthday))

Days until B'day contains following formula:

=IF([Next Birthday]=TODAY(),"Happy Birthday","has birthday in "&DATEDIF(TODAY(),[Next Birthday],"d")&" days")

To show only today birthday modify view and add filter Days until B'day contains Happy.