What does line 78 do?
The else statement cannot have a condition, plus realise that a year is a leap year or it isn't.
Remove the semicolon from line 70.
Also, consider putting the month data into an array & using a for loop to sum the values up to a given month. That way you can do the calculation in about 3 lines instead of 35. If you have a lot of repetition or tedious code, then there is probably a better way.
The leading zero's you have on the month values means that you have specified them in octal (base 8).
Line 75 can be written simply as
there are also the +=, -=, *=, /= operators (plus more) which you can use use if saying adding a number bigger than 1 for example:
MyNum += 5; // adds 5 to MyNum
MyNum *= 5; // multiplies MyNum by 5
Your leap year calculation isn't right - every 100th year isn't, but every 400th year is. This can be written as 1 statement.
Hope all goes well. :)