In the graph below you see the time zone difference between Greenwich Mean Time and Central Daylight 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). Central Daylight Time is the time zone of the central US and Canada, as well as most of Central America when observing daylight saving time in, with places like Winnipeg, Chicago, Dallas, Houston and Mexico City.
Usually it is preferable to schedule meetings in the afternoon for the person in GMT and before lunch for the person in CDT.
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.
Central Daylight Time is the time zone of the central US and Canada, as well as Mexico and most of Central America. It is five hours behind UTC and is observed during the summer months, between March and November. Sometimes the zone is referred to as CDST – Central Daylight Saving Time Zone. In the winter CDT becomes CST – Central Standard Time.
CDT is observed in the US, Canada, Mexico, Belize, Costa Rica, Guatemala, El Salvador, Nicaragua, Panama and Honduras i.e. all Central American countries. In the US it is only the states in the central US that observes CDT, from Wisconsin in the West to Tennessee in the East, and from Michigan in the North to Florida in the South. Similarly, only Canadian provinces in the middle of the country observe CDT. All of Mexico observes CDT, except the North West corner of the country.
US: Alabama, Iowa, Louisiana, Texas, Nebraska, Oklahoma, Illinois and many more.
Canada: Manitoba, Ontario (most parts), Saskatchewan (only Creighton and Denare Beach)
Mexico: Chiapas, México, Oaxaca, Yuca tán, San Luis Potosi and more.
CDT is the daylight saving time of Central Standard Time. There are only a handful of exceptions in this time zone that do not observe DST, so it is advisable to always check the exact location (e.g. using our time zone converter) instead of relying on time zone abbreviations.