Making Date Into Decimal Number?

How to make a date into a decimal number. For example, Dec 14 I need to convert to 11.45

Its basically the number of months and days that have gone by in that calender year. So the 11.45 is "11 months" have gone by and the .45 is the days that have gone by in the month of December. (the 14th day divided by 31 the total in December = .45)

So another example would be Feb 3rd. My conversion would be 1.10 (1 month has gone by in the calender and 3 days into the month, 3 / 28 = .10 so Feb 3rd is now 1.10)
June 20th = 5.66

Im creating a form so that my employees wont have to hand write these anymore and reduce all the human errors. Its to calculate income for my borrowers. I want them to be able to enter todays date and have excel convert that date into the decimal form. Then they can enter a Year to Date $ amount and that will calculate a monthly income.

< $ amount * decimal date = monthly income YTD>