GMT vs UTC Usage

[Scan125]

Well thanks to everyone for your replies.

I've looked at my various programs and whilst a simple GMT to UTC text change seems simple it is in fact quite complicated to implement under the covers due to all the logging, automatic saving, time scheduled tuning (HF / DriveR8) etc. Then there is all the User Manuals to update as well.

The change can certainly be done but it is not worth the risk and all the testing required to ensure nothing else gets broken.

May if in the future I decide to re-write the programs from scratch.

 

[air-scan]

If you are tweeting a nice DX catch I recommend the use of 'z' for 'zulu' time in which is the same as GMT and UTC since Twitter has limited characters per tweet. Mine would look like 1506z which is the time in GMT or UTC I type this post.
Also the difference isn't well reflected on websites with shortwave schedules which are GMT. Solar data related websites may use UTC. Either way means the same. No sense in trying to figure out any difference because they all are the same under real world use.

 

[bill4long]

PoTAYto PoTAHto, ToMAYto ToMAHto

 

[majoco]

I don't believe you can say that GMT is a time "zone", GMT by it's very name is a time. All zones are referenced to GMT by saying 'this zone is 'GMT+5' or whatever, but most countries have a local name for the time zone that they are in - we call ours "NZST" or NZDST" but any other country on our GMT+12 zone call call theirs whatever they like, Fiji, some of Kiribati, the Marshall and Line Island groups. Some are even straddling the date line, but any local administration can declare that all of their group will be on "GMT+ whatever". Interestingly, a couple of years ago Samoa decided that they wanted to be on the same day/date as New Zealand even though they are on GMT-11. This was because there were two non-business days with their major trading partner - on Sunday Samoa shuts down, but on their Monday, New Zealand was closed for business as it was now Sunday!

 

[dlwtrunked]

Much of this thread is somewhat inaccurate (as are some web pages). As some of us are old enough to remember, prior to 1972, "GMT" was the international standard for time (the name UTC did not exist before that). Though some web pages say it is a time zone, back then, when the name "GMT" was established, GMT was the international standard and was not just a "time zone". The distinction leading to the name change was that "UTC" was meant to mean a more accurate time system than any locally defined time-that is what caused the renaming.
Saying the difference is that GMT is a time zone is really not accurate despite some web pages saying that simply because it has a location in it(G-Greenwich) as it ignores the actually history of the terminology. In fact, technically GMT is not a time zone at all but is the mean solar time at the Royal Observatory in Greenwich, England. See NIST Time Frequently Asked Questions (FAQ)

 

[Scan125]

Well if I caused a little confusion when I originally started this post in saying " For those who are not sure what the difference is then very simply GMT is a time zone (as is GMT +/-n) and UTC is a time attributed to no zone. Appart from that 22:10:01 GMT is the same as 22:10:01 UTC and vica versa." then my apologies.

I did say "very simply" as I was trying to *simply* differentiate between GMT and UTC *as used/perceived)* in general terms.

You are correct in the GMT is not technically a time zone other but *WAS* a technical/scientific time "standard" reference/measured (as you say) at the RO in Greenwich based on an astronomical time scale.

However GMT usage is a time reference in the Greenwich geographical area/zone and other world geographical locations around the world have decided to "zone" their local time to GMT +/-n hours.

Of course today GMT and UTC times are exactly the same and based on the weighted average of a number of extremely accurate so call atomic clocks.