Question: I have two columns of year in excel sheet as year.months format (column first as 1.11 means 1 year 11 months) column second as 0.7 means 7 months). I need difference between two columns as year.months format. i.e., 1.11-0.7=1.4 means 1 year 4 months.

Answer: 
Working with DatedIF

Assume start date is in B1 and end date is in A1.

Step 1) Convert date

Convert the string to an actual excel serial date

In C1 and Use the following formula and copy to D1

```
=DATE(LEFT(A1,FIND(".",A1)-1),RIGHT(A1,LEN(A1)-FIND(".",A1)),1)

```

The conversion assumes the first of the month

Step 2) Determine the difference in months

Place the following in E1

```
=DATEDIF(D1,C1,"M") 

```

Note the start date need to be further back in time than the end date or you will get #NUM error.

Step 3) Convert back to your string format for y.m

Place the following in F1

```
=INT(E1/12)&"."&(E1-INT(E1/12)*12)

```

and combined into the uglyness of a single cell formula:

```
=INT((DATEDIF(DATE(LEFT(B1,FIND(".",B1)-1),RIGHT(B1,LEN(B1)-FIND(".",B1)),1),DATE(LEFT(A1,FIND(".",A1)-1),RIGHT(A1,LEN(A1)-FIND(".",A1)),1),"M"))/12)&"."&((DATEDIF(DATE(LEFT(B1,FIND(".",B1)-1),RIGHT(B1,LEN(B1)-FIND(".",B1)),1),DATE(LEFT(A1,FIND(".",A1)-1),RIGHT(A1,LEN(A1)-FIND(".",A1)),1),"M"))-INT((DATEDIF(DATE(LEFT(B1,FIND(".",B1)-1),RIGHT(B1,LEN(B1)-FIND(".",B1)),1),DATE(LEFT(A1,FIND(".",A1)-1),RIGHT(A1,LEN(A1)-FIND(".",A1)),1),"M"))/12)*12)

```
Let's say `A1=1.11` and `B1=0.7` then formula would be:

`=LEFT(A1;FIND(".";A1;1)-1)-LEFT(B1;FIND(".";B1;1)-1)&"."&(MID(A1;FIND(".";A1;1)+1;2)-MID(B1;FIND(".";B1;1)+1;2))`

[![enter image description here](https://i.stack.imgur.com/UC54d.jpg)](https://i.stack.imgur.com/UC54d.jpg)