Planning a meeting
Set the time in your own time zone, then add each participant's city. Aim for a time that falls between about 8 am and 6 pm for everyone; the “next day” and “previous day” labels warn you when it crosses midnight somewhere.
Cities, not abbreviations
Abbreviations like EST or IST are ambiguous and don't change with daylight saving. Choosing a city always gives the correct local time for the date you pick.