User talk:Joe

This is a test of the user notification system. When someone writes on your user talk page, you get notified. --Miike 18:17, 23 July 2008 (UTC)

Awesome! Check out the Powers of Commutative Elements in Semigroups‎ page, where this technique has just had its baptism! Okay so it's a bit of a weak proof but it shows how neat and compact it is. Be aware that I'm a neatness freak btw, readability of source code is 100% as important as readability of the end product, which explains my fussiness over formatting. --Matt Westwood 19:04, 19 October 2008 (UTC)

Awesome, looks good! --Joe 19:13, 19 October 2008 (UTC)

Yo, did you add Payne's signature manually, or did you log in to his account? --Cynic 17:06, 22 November 2008 (UTC)

manually, just looked at the timestamp from the history log. I can't get access to accounts, passwords are protected with MD5. --Joe 18:05, 22 November 2008 (UTC)

Hey, save it for April Fools Day Proof of the Week :D --Cynic 17:45, 26 November 2008 (UTC)

Very, very subtle. Still trying to put into words exactly what goes wrong and why ... --Matt Westwood 19:30, 26 November 2008 (UTC)

What to do?
For one "Topic" i must write one theorem with the respective proof? or can I write more than a theorem? For example the area of a triangle have alots of formulas then i have write a "topic" with each of the formulas or only in one "topic"

thk gamma

Good question, I guess what I would do would be either:
 * 1) Do a separate page for each one with good descriptive names and put them inside of a new area of triangle category inside euclidean geometry category, or
 * 2) put them all on one single page and use formatting similar to what I've boxed in below.
 * 3) Another thing would be to do the first option, then transclude all those separate proofs onto a single page using  to dump the content from that page. Then use idea 2 to organize them.
 * 4) The last thing I can think of is use an approach similar to Trigonometric Identities.

Theorems
For any triangle ABC with sides a,b, and c, the area of ABC has the following properties:

Area Equal to some formula
Statement

Some other statement wrt area of ABC
Statement ...

Proof that statement 1 is true
proof

Proof statement 2 is true
proof ...

Those are the only things I can think of. With something like that were's there several formula it's pretty well open ended what you want to do with it. If anyone else is reading this and has an opinion or idea please comment. Hope this helps! --Joe 03:27, 30 December 2008 (UTC)

Well, personally I think it makes sense to have separate pages and maybe transclude them. That way we can have a seperate page for Heron's Formula (or Hero's Formula if you prefer), since it at least belongs in Named Theorems.

For the moment, I would just put it up in whatever format seems most comfortable for you, and we can worry about organization later. --Cynic-(talk) 05:10, 30 December 2008 (UTC)

good call. --Joe 15:46, 30 December 2008 (UTC)

Geometry euclidian or analytic ?
well i have a new problem.. what happens if there is a theorem of euclidian geometry but the proof was made with "analytic".(by "anlytic" i understand, for me ,in geometry, is use vectors) --Gamma 22:43, 31 December 2008 (UTC)

The fact of a proof being valid in a flat space (as opposed to elliptic or hyperbolic) means (to me) that it's a Euclidean Geometry theorem. The fact that it's proved by a Cartesian method should not matter. Thoughts? --Matt Westwood 23:03, 31 December 2008 (UTC)

okokoooko i forget that we can put one topic in two difernt categorys =O -- Gamma 23:15, 31 December 2008 (UTC)

NUM pages
I actually think it makes more sense to copy and paste the message. That way people who are relatively new to wikis won't be confused by seeing when they edit their user talk page. That said, if you want to make a template, feel free. --Cynic (talk) 20:26, 10 March 2009 (UTC)

Rename request?
Hi, Joe. I was hoping you could change my username? I want to use my real one, that is, J D Bowen or J_D_Bowen.

Done! --Joe (talk) 23:43, 27 April 2009 (UTC)

Thank you! J D Bowen 19:07, 28 April 2009 (UTC)

New page?
Okay so you've proved $1<\gcd(x-y,n)<n$ and $1<\gcd(x+y,n)<n$ ...

Because $\gcd(x-y,n) | n$ then $\gcd(x-y,n) \le n$ anyway because of the nature of Integer Absolute Value Greater than Divisors.

So all this says is that $x-y \ne n$ or $n \mid (x-y)$, and $(x-y)$ is not coprime to $n$.

But I'm looking at this and surely $x^2\equiv y^2\pmod{n} \implies x \equiv \pm{y} \pmod{n}$?

So I'm not sure if the premise can ever be true in the first place.

I may be completely wrong - can you think of any $x, y, n$ such that $x^2\equiv y^2\pmod{n}$ and $x \not \equiv \pm{y} \pmod{n}$? --Matt Westwood 15:01, 24 May 2009 (UTC)

Goodness so it is. How about something like "Limits of GCD for Sum and Difference Congruent Squares" or something vague like that?

I'm wondering whether you can prove something stronger, but no worries ... --Matt Westwood 15:35, 24 May 2009 (UTC)

been away
In case you wondered where I've been, I had internet connection problems since Monday (stupid ISP). I'm back. --Matt Westwood 21:50, 18 June 2009 (UTC)

I was starting to get worried :p --Joe (talk) 11:40, 19 June 2009 (UTC)

Five Color Theorem
I think I finally got it sorted out fully. Take a look and let me know if it looks right so we can take it off wanted proofs. --Cynic (talk) 04:00, 30 June 2009 (UTC)

Looks good to me --Joe (talk) 01:58, 8 July 2009 (UTC)

I'm slowing down ...
Just in case you're worried I've died or something ...

I've gone about as far as I can go for the moment on the elementary stuff. Notes on the following:
 * I got tied up in knots and bogged down in the predicate logic stuff. I need to go away, do some reading, do some work and formulate the best way to proceed before I can go any further (and probably backtrack big time). Maybe someone else with a better background in formal systems might want to pick up on it. My own knowledge in this area is primitive and self-taught.


 * I have it in mind to do something to flesh out basic Graph Theory, but you already have someone on that particular case.


 * I could also continue with Euclid, but that's also being covered.


 * Then there's statistics and probability, which I don't like (despite the fact of it being merely an extension of boolean algebra -- strangely enough I've never seen that fact stated anywhere).


 * I have it in mind to start with some applied maths (after all, there's no point covering diffeqs without applications), but it's too big a job for me at the moment.

Basically, the current economic and industrial / professional climate being what it is, I'm going to need to work on some projects of my own for a while, as I really need to get some more strings on my bow / keep the bread and butter coming in.

I'll keep dropping in, and putting a theorem / biog / definition up here and there, and keep on with the tidying up, but I'm not going to be anywhere near as busy as I have been in the past year or so.

I've sent the same message to Cynic.

all the best --Matt Westwood 20:28, 26 July 2009 (UTC)

Sounds good, now the rest of us won't look so bad ;) --Joe (talk) 00:09, 27 July 2009 (UTC)

Re : Welcome
Thanks :) I spotted Tychonoff's Theorem on the Most Wanted List and thought I'd give it a go since I recently did an exam on topology. After quite some background stuff (required for the ultrafilter-approach I'm going to use) I'm almost ready to prove the theorem itself. Florian Brucker 14:09, 25 January 2010 (UTC)

Renaming
Was there any special thing you had to do to rename JD, or did you just move his old user page to the new one? --Cynic (talk) 05:27, 4 August 2010 (UTC)

Used this -- Special:RenameUser --Joe (talk)

Only available to bureaucrats. Can you rename me to Alecscooper Thanks much --Cynic (talk) 05:49, 8 August 2010 (UTC)

No prob --Joe (talk) 17:05, 9 August 2010 (UTC)

While you're about it, can I change my name to "prime.mover"? Pretentious moment coming on ... --Matt Westwood 18:43, 9 August 2010 (UTC)

Sure thing, is "prime.mover" the format you want? --Joe (talk) 19:23, 9 August 2010 (UTC)

Yes please --Matt Westwood 19:35, 9 August 2010 (UTC)

... thx bro --prime mover 18:50, 10 August 2010 (UTC)

email
I sent you a reply to joe@proofwiki.org last night, it ought to have reached you. If not then we have a problem to sort out. --prime mover 06:22, 3 February 2011 (UTC)

Community portal
... where's it gone? --prime mover 15:39, 4 February 2011 (CST)

email
... and what's my email password? Stick it into my home page, I can't get to my work email account till Monday! --prime mover 15:41, 4 February 2011 (CST)

Thx bro - we're in. --prime mover 02:44, 5 February 2011 (CST)

MathJax
Yes indeed.

Initial reaction:


 * The $\LaTeX$ looks so much sweeter, and includes significant new functionality, for which I say: Nice one.


 * The delimiter tags now allow dollar signs, which is extremely useful for pasting directly from conventionally-written $\LaTeX$ documents. It also significantly reduces the source code. Not sure if I prefer it to "math" delimiters, but the latter also work so no worries there - means it's still portable to other sites.


 * A couple of minor issues:
 * $\S$ and $\P$ no longer render as they ought: "Section" and "paragraph" markers, and $\O$ doesn't render any more.
 * We've also lost $\and$ and $\or$, for which we will have to go back to $\land$ and $\lor$ . This will mean lots of pages.
 * We now have $\mathscr ...$, so there's $\mathscr{ABCDEF}...$ available at last.

Is there a way, do you know, for defining / redefining $\LaTeX$ sequences, so that $\or$ will be interpreted as $\lor$ ?
 * I've answered this for myself by seeing what's in the sandbox. Can we make such a definition global?

Nice job. --prime mover 11:00, 6 February 2011 (CST)

... Other stuff: have you noticed how latex in a link is now blue? So you can actually put a formula in a link and it appears as a link. That's really, really good.

One minor point: $\!$ no longer appears to do a backspace. More research needed. --prime mover 11:05, 6 February 2011 (CST)

Another point: the "Equation" tag doesn't work too well when there's fractions in the mix - see Einstein's Law of Motion for a car-crash. --prime mover 11:27, 6 February 2011 (CST)


 * My guess is that if we decide to keep using MathJax, we'll have to ditch and use align. --Joe (talk) 11:31, 6 February 2011 (CST)


 * Aargh - that hurts. That really hurts. --prime mover 13:07, 6 February 2011 (CST)


 * Just have to do it one page at a time. --Joe (talk) 13:27, 6 February 2011 (CST)


 * Okay no worries, but it may take time to find the sweet spot. And we only need to fix the pages that are blatantly broken. --prime mover 13:30, 6 February 2011 (CST)


 * Maybe also add a note saying that is depreciated, or something. --Joe (talk) 13:32, 6 February 2011 (CST)

Okay then, one more thing ...

When you did this in the old code:

it used to indent it by a noticeable tab, thus offsetting code for presentation purposes.

But now what this does is center the equation on the page.

This doesn't look so good when it's rendered, specially when the text before it is short. You've got short text, then way over in the middle the equation, then the text at the left, then the equation in the middle ... Hard on the eye, and the flow is broken up.

What you can do to fix this is make it:
 * :$blah$

... so the browser thinks it's in-line text. But then you have to add \displaystyle to the equation, which feels unnecessary.

Is it possible to set "display" equations left justified as a site-wide default? I believe it's possible to do this in standard LaTeX documents, so I reckon it ought to be poss to do in MathJax. --prime mover 15:18, 6 February 2011 (CST)


 * Good question, I'll look into it later this evening. --Joe (talk) 15:25, 6 February 2011 (CST)

And something else: the "Explain" template also needs attention - doesn't work when there's latex in it. See Number of Distinct Conjugate Subsets for an example. --prime mover 16:12, 6 February 2011 (CST)

... See my talk page ... --prime mover 16:42, 7 February 2011 (CST)


 * MathJax suggestion (I don't know where else to put this): make MathJax left-align the LaTeX Equation Display environment.
 * The house style pretty much prohibits the LaTeX Display Equation environment (delimited as \ [ \ ]), because MathJax defaults center it. A simple configuration option can salvage this: setting the environment's CSS "text-align" attribute value to "left", as described here. It's located under the environment's selector (called ".MathJax_Display"), which is under "style" for each output processor. This change left-flushes formulas in the display environment to match house rules. I've tested this change on my client, and it appears to work fine. What we stand to gain is an environment that allows equation numbering and referencing (through \ label and \ eqref commands).
 * --L0mars01 (talk) 13:37, 24 September 2012 (UTC)

I'm okay with doing this if everyone else is as well. --Joe (talk) 13:40, 24 September 2012 (UTC)


 * Don't want it completely to the left, we want an appreciable gap at the left the size of a ":" command. Otherwise, yeah that would work for me - if we can fix it for that minor detail.
 * L0mars1: The usual accepted technique for talk pages is to add a new section at the bottom. Easier to follow the thread through chronologically. --prime mover (talk) 17:03, 24 September 2012 (UTC)


 * Minor detail can be fixed; I think this is a worthwhile addition to our collection of available techniques. The eqn and axiom templates could be amended to allow for configuring labels. --Lord_Farin (talk) 17:17, 24 September 2012 (UTC)

Three things
First, the mathjax doesn't appear to render at all on IE8 for me - I just see the raw text that would be inside the math tags, which is kind of a serious issue since so many people use IE...

Second, when I edit a page the bar with page, discussion, edit, history, etc gets covered weirdly (see here). Also, at 100% zoom the spacing seems to render weirdly on the mathjax in firefox 4 and chrome - setting the zoom to 110% makes it look alright, but it's not ideal to force users to correct that. Thoughts on any of these?

P.S. the block in the pre and nowiki tags at the top of your talk page is rendered in really small text, I have no idea why. --Alec (talk) 20:26, 7 February 2011 (CST)


 * I'm looking into IE8 now, I don't have a copy so I'll have to get back to you. As for the editing and that top bar, try changing your theme to the vector theme. --Joe (talk) 21:02, 7 February 2011 (CST)


 * More thoughts on the IE8 issue: your page seems to render the math fine, but all of the others that I've looked at in IE8 don't render the math. When I edit your page though, the math doesn't render in the preview of what the page looks like... The browser also shows that the site loaded with errors on page (see [[User:Alecscooper/IE8 Error|

here]]) for the errors). Hope that helps --Alec (talk) 15:05, 13 February 2011 (CST)


 * My turn to butt in ... Have you tried a page which is all dollar-delimiter LaTeX rather than pages which still use delimiters? The latter aren't always done properly. See the Recent changes page for pages I've touched recently, all of which have had the old ones removed. --prime mover 15:17, 13 February 2011 (CST)


 * Still doesn't render properly, but the dollar signs appear in the page text along with the latex (the math tags don't) --Alec (talk) 15:51, 13 February 2011 (CST)

Having played with it a bunch (hence the 40ish edits to my sandbox, I still have no real idea what's causing the problem. I've left it so my sandbox renders properly and my second sandbox doesn't, so if you can find differences between those two, that would be a good place to start... --Alec (talk) 15:01, 14 February 2011 (CST)

Can anyone check to see if IE is working now? --Joe (talk) 11:00, 15 February 2011 (CST)


 * Still a problem on my computer. I did find another page that renders correctly though: User talk:Gamma (and I created Test page, which renders properly, just to make sure it wasn't some weird behavior of the user talk namespace).  I'll go check on a school computer after lunch and make sure it's not just my settings spazzing somehow... --Alec  (talk) 11:51, 15 February 2011 (CST)

Equation Editor
I think I know what the problem is.

When you have two closing curlies together it thinks it's the end of a template. So what we can do is stick a space between any such pairs when we have a problem. See Secant Plus One over Secant Squared.

Another thing we may want to do is put the math tags into the template itself and inserting a "displaystyle" in there so as to make fractions come out in a decent size. Probably only in l and r templates, as the ll and rr and c and cc and o ones aren't necessarily usually math ones.

So we'd have:


 * align="right" |
 * align="right" |
 * align="center" |
 * align="left"  |
 * align="left"  |
 * align="left"  |
 * align="left"  |

... or something. I will experiment. --prime mover 15:55, 8 February 2011 (CST)


 * Yea, I put a message on your page about it earlier I think ... still not sure on a more elegant solution. --Joe (talk) 15:58, 8 February 2011 (CST)


 * Aha yes, I read it yesterday and it didn't register. I was tired. Now I know what you mean.


 * Check out Template:Newequation, and see how it works in Secant Plus One over Secant Squared. This is to get round the "displaystyle" bit. --prime mover 16:08, 8 February 2011 (CST)


 * I'll take a look at it later this evening!
 * P.S. I apparently just wrecked main page talk (half of it is in math mode). Will look to see what I've done later. --Joe (talk) 16:11, 8 February 2011 (CST)


 * ... okay then, check out Einstein's Mass-Energy Equation. Wikkid. --prime mover 16:43, 8 February 2011 (CST)
 * ... and fixed the Main Page talk - there was a dollar sign being interpreted as a LaTeX delimiter. Don't know how, but to fix it I turned it into $\$$. --prime mover 16:53, 8 February 2011 (CST)

MathJax - final verdict
Okay, I'm happy. The disadvantages are more than compensated for by the advantages. It looks like it may be another opportunity to revise what's there ...

One minor issue that I'm having trouble getting my head round: after you do a ctrl-V to paste, the cursor is in an indeterminate place, which certainly ain't on the page you're editing.

Another point to bear in mind is that " < /math > " delimiters don't work in transclusions. This is noticeable on the POTW (or was before I fixed it). No big deal though because we have a global search & replace. Which is wonderful. --prime mover 15:15, 9 February 2011 (CST)

Bots
Does this site support bots like Wikipedia does? I know nothing about this subject (haven't investigated, perhaps I should) but it ought to be straightforward to get a bot to search through all pages for instances of   and put a category marker on that page as "deprecated" like we got for stubs and tidy and explain and so on. Good idea? I'd rather it didn't automatically change them all to dollar because then there would be no opportunity to adjust the syntax. --prime mover 00:50, 11 February 2011 (CST)


 * Bots are indeed supported ... if I get some free time I'll make one. If you want to make one let me know and I'll give it access. --Joe (talk) 06:12, 15 February 2011 (CST)

Trouble Viewing Pages
Joe, I am new here. When I view a proof I see the Latex code. Is this normal or do I need to do something to see the symbols produced by the code? Thanks! Chris


 * Are you by any chance using Internet Explorer? The $\LaTeX$ rendering software we're using is having trouble rendering on IE at the moment. I would recommend trying either Chrome or Firefox if this is the case. --Joe (talk) 22:35, 13 February 2011 (CST)

The WelcomeBot
... and I was just about to add a NUM to the WelcomeBot, then I woke up properly this morning.

Presumably there will no longer be a need to add the NUM to new users? --prime mover 00:18, 2 September 2011 (CDT)
 * Yep, still need to finish coding it though. --Joe (talk) 09:25, 2 September 2011 (CDT)
 * There's a slightly later version of the Welcome page that Alec and I have been using - it puts Welcome in H2 (consistent with the rest of the site) and also suggests checking the house style (a vain attempt on my part towards getting new submitters to honor some sort of feeling for consistency ... never mind). And the autosig might want to go to a different page, but I don't know what would be particularly appropriate. --prime mover 11:48, 2 September 2011 (CDT)
 * Feel free to edit User:WelcomeBot/UserMessage, I'm still in the process of ironing out some kinks in the code. --Joe (talk) 11:50, 2 September 2011 (CDT)
 * I might be tempted ... see if I can get the wording to be a mathematically significant number of characters. If I can add 22 characters that would make it 1089. Woot.
 * Probably won't think about it tonight, too tired, been a busy week. --prime mover 14:19, 2 September 2011 (CDT)
 * Ok, I think I've ironed out all the kinks. Basically all the bot does at the moment is check to see if the user talk page is blank and if so, add the message. I have it running every 15 minutes to check for new users. --Joe (talk) 17:30, 2 September 2011 (CDT)

How easy would it be to add a time and date to the User Welcome message? Interesting to know when a particular user joined. Not a problem if it raises technical difficulties, there are of course other ways (just press on "View History"). Just a thought. --prime mover 05:50, 16 October 2011 (CDT)
 * Done. I haven't had a chance to test it. So lets hope it works. --Joe (talk) 08:58, 16 October 2011 (CDT)

"Proofs" that 1 = 2
Hi. Just wanted to know where's the fallacy in the "proof". I'm guessing the second step isn't true for non-integers, therefore the RHS cannot be differentiated like Taylor series...

Collapsible section
I think I have finished the functional part. Access to MediaWiki:common.js and MediaWiki:common.css would allow me to formally introduce it on PW (though some styling and the like is still necessary). Also see User_ Talk:prime.mover for the latest updates. It could also be added to MediaWiki:Edittools. --Lord_Farin 17:04, 17 October 2011 (CDT)
 * Sure, I'll give you temporary sysop privileges. If you stay around, we'll see about keeping them :) --Joe (talk) 08:38, 18 October 2011 (CDT)
 * Done --Joe (talk) 08:40, 18 October 2011 (CDT)
 * The functionality has been implemented. The templates are Template:begin-foldable and Template:end-foldable. --Lord_Farin 12:48, 18 October 2011 (CDT)
 * Super professional job mate. --prime mover 14:29, 18 October 2011 (CDT)

Rogue newline in WelcomeBot message
Check out the latest WelcomeBot message. It contains "Cheers!\n:-- Your friendly ..." so it hasn't put the newline in at all. (Should it not be &lt;br/&gt; instead of \n? --prime mover 14:26, 27 October 2011 (CDT)
 * Should be fixed now, I thought the api would convert the perl \n into a line break before parsing. Guess not. --Joe (talk) 15:02, 27 October 2011 (CDT)
 * Yep, sort of almost worked - just need to get it to make that colon at the start of the line treated as a tab indent. --prime mover 17:06, 27 October 2011 (CDT)

MathJax/dollar sign rendering
Ran into a problem today when I was trying to set myself up for writing tableau proofs. The problem arises as follows:

On eg. User:Lord Farin/Tableau Proof Rules/Conjunction, the code part is rendered correctly (that is, no MathJax interfering).

However, on User:Lord Farin/Tableau Proof Rules, when looking at the code bits (except for the first, non-transcluded one), there has in fact been MathJax processing of the dollar signs, despite the nowiki tags.

Obviously, the problem is in the transclusion. Is there any way around this except not using transclusions? I was thinking about an extension but I have a feeling I am not up to that part of MediaWiki now. Any thoughts? --Lord_Farin 08:42, 10 November 2011 (CST)


 * I'm not sure how to deal with this at the moment. When I get some free time I'll dig into it. --Joe (talk) 20:32, 24 November 2011 (CST)


 * Wouldn't bother even trying. This only affects maintenance pages and stuff. In presentation pages it shuldn't make a difference. --prime mover 00:13, 25 November 2011 (CST)

Database Dump
Any chance of being able to do a database dump for Arided, as discussed on main news page? Or point me towards the appropriate directory where the tools live, so I can do it? Thx ... --prime mover 02:41, 16 April 2012 (EDT)


 * I've been following this stuff all weekend, but didn't get a change to comment yet. I'll dump the database shortly. --Joe (talk) 07:00, 16 April 2012 (EDT)

More technical problems
--Dfeuer (talk) 04:42, 8 March 2013 (UTC)


 * Let me add to that:

Warning: apc_store: Unable to allocate memory for pool. in /home/proofwiki/www/wiki/w/includes/objectcache/APCBagOStuff.php on line 59

Warning: apc_store: Unable to allocate memory for pool. in /home/proofwiki/www/wiki/w/includes/objectcache/APCBagOStuff.php on line 59


 * Memory leaks, perhaps? &mdash; Lord_Farin (talk) 09:38, 8 March 2013 (UTC)

Any idea when this is occurring? --Joe (talk) 11:28, 8 March 2013 (UTC)


 * It seems to occur at random; currently it's gone. Check https://bugs.php.net/bug.php?id=58982, and the error logs. &mdash; Lord_Farin (talk) 11:44, 8 March 2013 (UTC)


 * Happened to me when I had a lot of pages open at once. But then it didn't go away when I shut them down. It did not appear adversely to affect behaviour of PW. I use Google Chrome. --prime mover (talk) 12:39, 8 March 2013 (UTC)


 * It'll happen a few times in a row, then go away, then come back. No idea if there's a pattern. --Dfeuer (talk) 17:02, 8 March 2013 (UTC)

These issues should all be sorted out now! As well as it not spewing errors onto the page. Basically the php cache wasn't big enough and was getting filled. It was happening with the old system as well, just buried in a mountain of logs. --Joe (talk) 21:26, 8 March 2013 (UTC)

Technical problems with graphics upload
Can't upload graphics at the moment: Could not create directory "mwstore://local-backend/local-public/3/3c".

Similar to what happened a while back - write permissions? --prime mover (talk) 06:44, 19 May 2013 (UTC)
 * Hrm... probbably... I'll go take a look. --Joe (talk) 11:59, 19 May 2013 (UTC)
 * Try now. --Joe (talk) 12:03, 19 May 2013 (UTC)


 * That seems to have worked. Thx. --prime mover (talk) 13:36, 19 May 2013 (UTC)