Time Zone Converter

Why time zones are harder than adding hours

If time zones were whole hours apart and never changed, mental arithmetic would be enough. They are not. India runs 30 minutes off the hour, Nepal is 45 minutes off, and daylight saving shifts many zones twice a year on dates that differ by country. That last part is what causes most mistakes: a meeting scheduled correctly in March quietly becomes wrong in April because one side moved and the other did not.

Scheduling across zones without confusion

• Always state the zone with the time. Nine in the morning means nothing on its own.
• Use the other person's zone when you propose a time, not your own.
• Watch out for the date changing. Late evening in Asia is the same day's morning in the Americas.
• Be careful near daylight saving changeovers, since the gap between two cities can move by an hour.

The abbreviation problem

Time zone abbreviations are genuinely ambiguous. IST is Indian Standard Time, Irish Standard Time and Israel Standard Time. CST covers a zone in North America and a different one in China. BST is British Summer Time to some and Bangladesh Standard Time to others. Naming the city removes the ambiguity entirely, which is why saying nine in the morning Karachi time is safer than any set of letters.