LHC@home

I'm in the UK, which is using GMT. AFAIK GMT and UTC are the same time.
On one of my machines, I have a task running which has a deadline of 13:44:32 28th Nov local time (ie. GMT).
Yet in my list of tasks on the LHC website, that same task has a deadline of 13:44:32 29th Nov UTC.
Why the 1 day difference?
The task is here, https://lhcathome.cern.ch/lhcathome/results.php?hostid=10620041
The other task for that machine is also a day out.
And in fact every task for my other machine: https://lhcathome.cern.ch/lhcathome/results.php?hostid=10619354
I've checked my Einstein tasks, and those show the correct time.

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That's the way it has been here for ages now. The subject is raised once in a while but nothing has been done about it.

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I was wondering if it affected deadlines. Presumably the server will think I have one more day to complete a task than my client does. I guess it's better than the other way round.

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Timestamp comparison on a linux host


Classical native task (SixTrack)

Client timestamps

client_state.xml
<received_time>1572352921.653704</received_time>

date -Ru --date='@1572352921.653704'
Tue, 29 Oct 2019 12:42:01 +0000

BOINC Manager (local time Germany)
Di 29 Okt 2019 13:42:01 CET


client_state.xml
<report_deadline>1572927254.000000</report_deadline>

date -Ru --date='@1572927254.000000'
Tue, 05 Nov 2019 04:14:14 +0000

BOINC Manager (local time Germany)
Di 05 Nov 2019 05:14:14 CET



Server timestamps

Sent 29 Oct 2019, 12:42:00 UTC
Corresponds to the client timestamps

Report deadline 6 Nov 2019, 4:14:14 UTC
1 day more.
Might be due to a grace period that (IIRC) can be configured at the BOINC server.
Don't know if this option is used here.




Vbox task (CMS)

Client timestamps

client_state.xml
<received_time>1572379023.814736</received_time>

date -Ru --date='@1572379023.814736'
Tue, 29 Oct 2019 19:57:03 +0000

BOINC Manager (local time Germany)
Di 29 Okt 2019 20:57:03 CET


client_state.xml
<report_deadline>1574971023.000000</report_deadline>

date -Ru --date='@1574971023.000000'
Thu, 28 Nov 2019 19:57:03 +0000

BOINC Manager (local time Germany)
Do 28 Nov 2019 20:57:03 CET



Server timestamps

Sent 29 Oct 2019, 19:57:03 UTC
Corresponds to the client timestamps

Report deadline 29 Nov 2019, 19:57:03 UTC
1 day more.
Might be due to a grace period that (IIRC) can be configured at the BOINC server.
Don't know if this option is used here.


BTW:
UTC and GMT are not the same by definition (but they are from a practical point of view).

I guess a grace period makes sense, perhaps LHC were receiving too many tasks slightly overdue. They need the answers back on Friday, so they tell the client to get it done by Thursday to speed it up. Or very long tasks that were miscalculated how long they'd take could still get credit that way.

How does UTC differ from GMT? At this precise moment, GMT and UTC are both 9:16PM on the 29th October. And they are always identical. It's just two names for the same thing.

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At this precise moment, GMT and UTC are both 9:16PM on the 29th October.

Yes, they show the same value.

And they are always identical. It's just two names for the same thing.

No. They are based on different definitions.

As I already wrote:
It has not much practical meaning here.

https://en.wikipedia.org/wiki/Coordinated_Universal_Time
https://en.wikipedia.org/wiki/Greenwich_Mean_Time

Sorry, I still don't know the difference. I'm not arguing with you, I'm interested to know what the difference is. Both those links say they are "mean solar time". So what's the difference?

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... I'm interested to know what the difference is ...

From the articles already linked:

GMT
...mean solar time at the Royal Observatory in Greenwich, London, reckoned from midnight. ... it cannot be used to specify a precise time unless a context is given.

English speakers often use GMT as a synonym for Coordinated Universal Time (UTC). ... but this meaning can differ from UTC by up to 0.9 s. The term GMT should not thus be used for certain technical purposes requiring precision.


UTC
The current version of UTC is defined by International Telecommunications Union Recommendation (ITU-R TF.460-6), Standard-frequency and time-signal emissions,[4] and is based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the slowing of the Earth's rotation.

UTC does not have daylight saving time, GMT does.

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UTC does not have daylight saving time, GMT does.

That's not true. In summer, the UK does not say "we are using GMT", we say "we are using BST" (British Summer Time).

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... I'm interested to know what the difference is ...

From the articles already linked:

GMT
...mean solar time at the Royal Observatory in Greenwich, London, reckoned from midnight. ... it cannot be used to specify a precise time unless a context is given.

English speakers often use GMT as a synonym for Coordinated Universal Time (UTC). ... but this meaning can differ from UTC by up to 0.9 s. The term GMT should not thus be used for certain technical purposes requiring precision.


UTC
The current version of UTC is defined by International Telecommunications Union Recommendation (ITU-R TF.460-6), Standard-frequency and time-signal emissions,[4] and is based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the slowing of the Earth's rotation.

So what they're trying to say is UTC is far more precise and doesn't allow interference from the earth wobbling etc?

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UTC does not have daylight saving time, GMT does.

That's not true. In summer, the UK does not say "we are using GMT", we say "we are using BST" (British Summer Time).

OK. Good to know.

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So what they're trying to say is UTC is far more precise and doesn't allow interference from the earth wobbling etc?

Right.