It shifts the time system forward one hour for part of the year
Ancient systems included varying the length of hours at different times of the year. The modern system of shifting the time observed is currently used in much (although not all) of Canada, the USA, Europe, Middle East, Central and South America, the Caribbean, Australia, Oceania, and in two countries in Africa, in Greenland and in New Zealand. It has been observed and abandoned in much of the rest of the world. It has been made permanent i.e. year round, in some jurisdictions such as Argentina, Chile, Iceland, Singapore, Uzbekistan, Belarus and Turkey, though Russia which had made it permanent shifted back in 2014 to alleviate what became the unpopular and very long morning darkness in winter.
