While Microsoft Excel automatically reformats time values as hours and minutes, you can manually change the cell's time format to display the seconds as well.

Pro Tip: To open formatting options, just select the cell (s) you want to format and press Ctrl-1 (Mac: Command-1). This actually works for anything in Excel: charts elements, images, etc.

You can change the date & time format in Google Sheets & Excel Online using this guide. Use different date & time formats in spreadsheets.

Open the Excel 2010 file that you want to make format changes to. Select the top-left cell in the range of cells that you want to change to the accounting format.

However, if you paste a differently formatted date, Excel accepts the source formatting. To further complicate the situation, Excel changes the format of the target cell to that of the pasted value!