Usually, our applications must work in different nations with specific rules, languages, currency, number codecs, etc. I mean every country may need its own regional settings so each point needs a particular treatment.
The earth spins around itself at the rate of 1 rotation per 24 hours, it implies that every area on the planet has its noon at a unique time primarily based on the longitude of its location.
In 1884, the Worldwide Meridian Convention chose a meridian to be employed as a common zero of lengthyitude and standard of time reckoning all through the world. It resulted within the suggestion of the Greenwich Meridian because the prime meridian. In addition, it has established to have 24 totally different time zones because the earth rotates 360 degrees in 24 hours, 15 degrees lengthyitude each hour. It means every time zone is 15 degrees longitude other than each other.
The next map can assist us to make clear these criteria:
The Greenwich Imply Time (GMT) is the primal meridian with 0 degrees.
In East of Greenwich (Proper), each 15 degrees is a time zone +1 hour.
In West of Greenwich (Left), each 15 degrees is a time zone -1 hour.
In theory, to handle time zones would not be difficult following previous criteria and it works properly for all cases. We’d always be able to calculate the native time in any place only based on its location, but NOT. Time zones can change:
International locations and territories that cross these artificial lines (shown on the map) determined to draw these ones differently. e.g. China is the biggest country with only 1 time zone, but it ought to have 5 time zones.
Some international locations set clocks forward by one hour within the spring and set clocks back by one hour in autumn (DST).
Time zones are set by Governments, but governments typically change their minds.
What is GMT?
The primal meridian/primary time zone.
Greenwich Mean Time or GMT is the clock time at the Royal Observatory in Greenwich, London.
GMT is no longer a time standard.
What’s UTC?
A Standard, Not a Time Zone.
Coordinated Universal Time or UTC is the first time customary by which the world regulates clocks. It makes use of highly exact atomic clocks mixed with the Earth’s rotation.
This is the successor to GMT.
What’s a Time Zone?
A time zone is a geographic area where the identical commonplace time is used (real place on the surface of the Earth). It implies that it follows the identical native clock, and abides the same set of timekeeping rules.
A time zone is NOT an offset from GMT or UTC. The offset is simply one characteristic of a timezone. Additionally, more than one offset would possibly apply, at different instances of the year. e.g Summertime and Standard Time.
What is DST?
DST is the apply of advancing clocks during warmer months in order that darkness falls later each day in line with the clock. It means to set clocks forward by one hour within the spring and set clocks back by one hour in autumn in order to return to straightforward time. It was first applied for Germany in the course of the first world war with a view to save energy.
This follow is still utilized in North America and Western Europe, but Russia and most of Asia and Africa nations don’t use DST.
e.g. MST and MDT
Mountain Commonplace Time = UTC -07:00
Mountain Daylight Time = UTC -06:00
or GMT and BST
Greenwich Mean Time = UTC +00:00
British Summer time Time = UTC +01:00
There are two transitions, in the spring when DST takes impact, there is an hour in local time that does not exist, and a day that is only 23 hours lengthy (transition starts). In the fall the opposite happens a whole hour occurs twice on the identical day and that day is 25 hours lengthy (transaction ends). It can be defined better with this schema.
Daylight saving time shows us that we can’t decide local time based only on location. We now have to know if daylight saving time was in impact or special cases that apply.
Time zones can change
Governments typically change their minds, this is the main reason why time zones guidelines change. Time zones are set by Governments so it is predicted surprises and oddities. It’d occur for various reasons comparable to commerce, non secular observations, political posturing, rise up, etc.
It implies that the time zone is decided by law so it is able to modify DST Guidelines, transitions, offsets, and alignments.
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