In the graph below you see the time zone difference between Greenwich Mean Time and India Standard Time. Drag the bubble to adjust the time and to see the corresponding time in the other time zone.
Greenwich Mean Time is the time zone of the 0 meridian, located in London, United Kingdom, including cities like London, Lisbon and Dublin (in the winter). India Standard Time is the time zone of India, with places like New Delhi, Mumbai, Bangalore, Kolkata and Colombo.
Usually it is preferable to schedule meetings before lunch for the person in GMT and in the afternoon for the person in IST.
GMT, or Greenwich Mean Time, is the zero when it comes to time zones – they are all counted from the zero meridian that runs through the village of Greenwich.
While both the UK and Portugal are officially on GMT you need to pay attention to whether they are actually observing it or are using their own. Britain in the summer for example use British Summer Time – which is different than GMT.
London, Lisbon, Dublin, Edinburgh
GMT does not observe DST as it is the zero hour time zone – it never changes.
India, Sri Lanka
Delhi, Colombo, Kolkata and Mumbai
This timezone does not observe daylight saving time so the time difference always stay the same. You however need to pay attention to if the other time zone is observing DST as this will make a difference.
IST can also refer to Irish Standard Time or Israeli Standard time, but most of the times it is India that is being referred to – just make sure to double check this before you send that calendar invite!