Time zones and daylight saving are handled correctly
An event abroad happens at the local wall-clock time there, not at your time. That is why this tool works out the target from the date, time and time zone you choose, including daylight saving changes. For example, a launch at 09:00 in New York lands at a different hour in Jakarta depending on the season.
The time left is calculated from your device’s system clock, so it stays exact while the tab is in the background. If your device clock is off, the countdown is off too.