elapsed time
Technical term used in computing, engineering, and timing contexts to refer to the amount of time that has passed from a starting point.
Display the elapsed time of the program in milliseconds.
経過 is a more general noun meaning 'passage' or 'progress', while 経過時間 specifically refers to the measured elapsed time.
所要時間 refers to the required or expected time to complete something, whereas 経過時間 is the actual time that has already passed.
Compound of 経過 (passage, progress) and 時間 (time). The exact historical derivation is uncertain, but the term is a straightforward technical compound.