Sick leave calculation

Hey guys,

I have tried a formula to count the sick leave taken but i realize
that my formula is wrong b in my company the balance of my sick leave
will be restarted each time the employee completes the year so i
messed up

please help this is the formula that i have used

C=Starting Date

and this is the sick leave schedule :
3months to 2 years:15 days
2 years tp 4 years :30 days
4 years to 6 years: 45 days
6 years to 10 years : 60 days


=IF(TODAY()-C6>6*365,60,IF(TODAY()-C6>4*365,45,IF(TODAY()-
C6>2*365,30,IF(TODAY()-C6>0.25*365,15))))


please advise
.