By input “=now()” (without a quote) you can get realtime date and time in excel spreadsheet.The date and time that are used are taken from the computer’s system clock.The formats for Date, Time, and Special can be set to conform to different locales.
Select the cells you want to format.

1.On the Format menu, click Cells, and then click the Number tab.
2.In the Category box, click either Date, Time, or Special.
3.In the Locale (location) box, select a locale to see sample formats for that locale in the Type box.
4.Select the desired number format from the Type box.
5.Click OK.
These may update the date and time each time you open the workbook.