If you stop the timer, I think it stops forever... I mean until you start it from somewhere else. But yes, the Timer is the most accurate in this case, if we really care about the time. Because we can look at the ticks, but they can come very fast or too slow.
But there is another way to measure the time. If you have datetime variable and you save some time in it, which actually looks like this: https://www.epochconverter.com/, then in the future you can calculate what is the difference between the current time and that old saved time. The difference will be in seconds. I think it was seconds in MQL, because sometimes it could be in milliseconds (x1000).
In MQL you can use the TimeCurrent() or TimeLocal() function if it's easier for calculations.