When I am copying partial text from one cell and pasting into another what I am pasting is separating into multiple cells.

Example:

Copying "June 15th" from a cell containing "Little Timmy's Birthday is June 15th", it pastes into two cells "June" and "15th".

Could there be a setting I have inadvertently changed? I have used the text to columns feature this morning splitting by space in another workbook, but I don't know why that may have carried over to when I use a simple Ctrl+C and Ctrl+V.