Define two calculation fields:
MonthHire: Month ( StartdateField )
DayHire: Day ( StartDateField )
You can then sort by MonthHire, then by DayHire.
You can compute the next anniversary date with this unstored calculation:
Let ( T = Get ( Currentdate ) ; Date ( MonthHire ; DayHire ; Year ( T ) + (MonthHire > Month ( T ) and DayHire > Day ( T ) ) ) )
+ (MonthHire > Month ( T ) and DayHire > Day ( T ) )
adds 1 to the year if the current date is after this year's anniversary date.