All the observed world time zones are listed by country (or territory) in the table below. There are independent states with multiple time zones, and the record-holder is France with 12 zones, but 11 of them are used in overseas areas and only one in the country’s mainland. The situation is the same in the United Kingdom, Denmark, New Zealand, Netherlands.
The countries with multiple time zones in the mainland area (some of them also have the insular territories) are Russia, USA, Canada, Australia, Mexico, Brazil, Indonesia, Kazakhstan, Mongolia, the Democratic Republic of the Congo, Kiribati, Micronesia, Chile, Spain, Portugal, and Ecuador.
The Daylight Saving Time (DST) is widely used in Europe and North America, and also in some parts of Africa, Australia, South America. It helps to make the daylight duration longer in summer by setting clock 1 hour forward in the spring (start of DST period) and setting them 1 hour backward in autumn when the DST period is over.
Alphabetical list of countries and territories with their standard time zones and DST