Microsoft Excel's Month and Weekday functions output numeric values for a given date. The Month function results in the month numbers, such as "3" for March or "12" for December.

First, I need Excel to work out how many full months have elapsed so far, so that when I use OFFSET, I can use this figure to tell Excel how far from the starting point I need to offset.

You should have experience with Excel before trying to use formulas to calculate what day of the week the 15th of a given month is, and you have several options to do this.

In Microsoft Excel, you can convert a number into a fraction using the Fraction format. Learn how to display Numbers as Fractions in Excel.