c = 42;         // current days leave from past
a = 20;         // number of days leave per year
m = 12;         // current month
n = 31;         // current day in month
d = 12;          // number of days leave taken in year
x = 1;          // is leap year 0 no  1 yes

p = 
((If[1 <= m, 1, 0] * 31) - (31 - If[1 == m, n, 31])) + 
If[x == 0, ((If[2 <= m, 1, 0] * 28) - (28 - If[2 == m, n, 28])), ((If[2 <= m, 1, 0] * 29) - (29 - If[2 == m, n, 29]))] + 
((If[3 <= m, 1, 0] * 31) - (31 - If[3 == m, n, 31])) +
((If[4 <= m, 1, 0] * 30) - (30 - If[4 == m, n, 30])) +
((If[5 <= m, 1, 0] * 31) - (31 - If[5 == m, n, 31])) +
((If[6 <= m, 1, 0] * 30) - (30 - If[6 == m, n, 30])) +
((If[7 <= m, 1, 0] * 31) - (31 - If[7 == m, n, 31])) +
((If[8 <= m, 1, 0] * 31) - (31 - If[8 == m, n, 31])) +
((If[9 <= m, 1, 0] * 30) - (30 - If[9 == m, n, 30])) +
((If[10 <= m, 1, 0] * 31) - (31 - If[10 == m, n, 31])) +
((If[11 <= m, 1, 0] * 30) - (30 - If[11 == m, n, 30])) +
((If[12 <= m, 1, 0] * 31) - (31 - If[12 == m, n, 31]));

z = (c + (((a / (If[x == 0, 365, 366])) * 7) * (p / 7))); 
N[z, 10]