|Well, your use of the word "format" is still confusing.|
You don't need to "format" J15 to display text, you can use an IF function:
=IF(DAY(A1) = 27, "specific text", "")
J15 will display an empty cell except in the 27th of each month.
Using an IF function is not considered "formatting" the cell.
If you really want to format J15 to display the text on the 27th, then you could use Conditional Formatting in this manner:
1 - Put your "specific text" in J15.
2 - Format the cell such that the font color matches the background color.
3 - Use the Conditional Formatting rule I offered above (=DAY(A1) = 27) and set the Font Color (within Conditional Formatting) to be something other than the background color of the cell.
On the 27th of each month the Font Color of J15 will change to the color you chose and the text will appear. On every other day, the Font Color will match the background color of the cell and won't be seen.
Click Here Before Posting Data or VBA Code ---> How To Post Data or Code.