NOW returns the current date and time and updates every time the sheet recalculates. For a timestamp that stays fixed, press Ctrl+; then Space then Ctrl+Shift+;.
Syntax
=NOW()
Examples
Example 1
=NOW()
Shows something like 12-Jul-2017 14:35 (format the cell to show time).
Example 2
=(NOW()-A2)*24
Hours since the ticket in A2 was opened.
Example 3
=IF(NOW()>B2, "Late", "")
Flag deadlines that have passed, including the time of day.
Common errors and fixes
You see
Why, and the fix
Value keeps changing
That is how NOW works. Paste as values, or use the keyboard shortcut for a fixed time.