To subtract time in Excel, you can use the subtraction operator (-) to subtract two times or use the TIME() function to subtract the time in one cell from the time in another cell. For example, to subtract the time in cell A1 from the time in cell A2, you can use the following formula:

=TIME(A2-A1)

If you want to subtract the time in cell A1 from the current time, you can use the following formula:

=TIME(NOW()-A1)