How to get the ISO time in 3 days with javascript?
Add days to JavaScript Date
Prove normal matrix is 4th power of some self-adjoint matrix Let $A\in\mathbb{M}_n(\mathbb{C})$ be a matrix of order $n\geq 2$. Let $p_A(x) = (x-\lambda_1)\cdots (x-\lambda_n)$ be the characteristic polynomial of $A$ such that all $\lambda_i$ are positive real numbers.  Suppose that $A$ is a normal matrix. Prove that one can write $A=G^4$ for some self-adjoint matrix $G$.  My thinking is that since $A$ is normal, by Principal Axis Theorem, we have $A=UDU^\ast$, where $U$ is a unitary matrix and $D$ a diagonal matrix. However, I fail to see how to proceed. Could anyone help me out? $IS \mid JS$ implies that $I\mid J$ where $I$ and $J$ are ideals of a number ring contained in another number ring $S$ Conformally Map Region between tangent circles to Disk $R$ is commutative, $I$,$J$ are ideals, $I+J=R$, then $IJ=I\cap J$ If $R$ is a commutative ring and $I$ and $J$ are ideals s.t. $I+J=R$ then show that $IJ=I\cap J$.  I've already shown that $IJ \subset I\cap J$, now I need to show the reverse inclusion.   I'm a bit lost, so far i'm just figuring out what pieces I have to work with.  Such as:  $\forall r\in R$ $\exists i\in I ,j\in J$ s.t. $i+j=r$  $\forall ij\in IJ$, $ij=i_1$ and $ij=j_1$ for some $i_1\in I$, $j_1\in J$.  Also, if I let $x\in I\cap J$, then $x=i_2=j_2=i+j$ for some $i_2\in I$, $j_2\in J$  Anyone, having problem getting to the conclusion here, thanks in advance I use the Stack Exchange sites very often to find solutions to problems and help me with decision-making.  In some sites I have asked question and received answers, and I have more than 15 reputation. On Stack Overflow I have always found answers to my questions and never needed to post a question (avoiding duplicate questions). However, I would like to vote for the answers that helped me but I do not have the ability to do that, due to low reputation.  Posting a question or answering an answer on each site seems like the only way to get enough reputation.  Since I have no input to give in these areas unless they will be counted as duplications, many answers that I have already used are missing my vote.  I suggest to take into account all of the reputations from all Stack Exchange sites for voting, or thinking about a different way to allow votes. Wine or virtual machine (VirtualBox) to run apps (eg. Photoshop) I am wondering if it will be better (stability, convenience and speed) to run apps like Photoshop with Wine or a virtual machine like VirtualBox? Closed unit disk homeomorphic to $\mathbb{R}^2$? I've already shown the existence of a homeomorphism between the open unit disc and $\mathbb{R}^2$ and now I'm trying to work out whether the closed unit disc is homeomorphic to $\mathbb{R}^2$ or not. Clearly the only real difference is the fact it includes the points actually on the circle, but because the continuous, invertible, bijective map I defined for the open disc was $\dfrac{x}{1-|x|}$ this clearly is not defined for the points on the line.   Intuitively I'm thinking it's not possible to form a homeomorphism with the closed disk precisely because of these points on the circle but can't really form a decent argument. I was thinking along the lines of showing that the non-open, closed subset $\bar{D}(0,1) \backslash D(0,1)$ (which is just the set of points on the actual circle i.e the boundary/frontier of the closed disk) can't possibly bijectively map to a closed subset of $\mathbb{R}^2$ - which clearly would have to be the case in a homeomorphism.   Any advice would be greatly appreciated. How to setup a restricted SFTP server on Ubuntu? I would like to know how to set up root, sudo, sftp-only user accounts which won't be required public key authentication at log in. I would also like to know how to set up sftp-only users' home directories where they can't access upper level other directories. I've got a domain that I apparently forgot to set a preferred domain for, so I just tried to do it. Webmaster Tools instead popped up a little box:     Part of the process of setting a preferred domain is to verify that you own http://www.example.com/. Please verify http://www.example.com/.   I'm running into some problems following these instructions:   As far as I can tell I already did verify sometime in the past. There's a TXT DNS record with the gibberish Google tells you to set for it that I couldn't have come up with myself. …and nothing is telling me this information is bad. So let's assume the site is somehow not actually verified. All  instructions start with "click the Manage Site button next to the site you want, and then click Verify this site." That button doesn't even exist on my screens. (It presumably goes away when you successfully verify?) Those instructions were all updated pretty recently, and the DNS one in particular just a couple weeks ago so it seems a bit unlikely they're inaccurate.   I am not using Apps, and won't be, so can't try out the verification .   Note that I also have another domain that I have not done any verification for which is showing the same behavior(no such button, being told to verify when it seems impossible etc.) so something appears to just be broken.  I already have a no-www process in place server-side, so we can skip that. I'm just trying to get the box checked off in GWT.  If I don't get any resolution, I'll eventually scrap the TXT record and see if the site gets un-verified(or whatever since it thinks it isn't), and see if I can just restart the process.  It's not urgent so I'm just trying to figure out if I've gone blind to something or what. Did the button move? With markdown, you can use some dashes for headings. For example, this: Hello ---- this is some other text  renders as this: Hello this is some other text This is fine and works well. When I want to quote that text is when the problem arises, since this Markdown: &gt; Hello &gt; ---- &gt; this is some other text  When written down shows well in the preview but not when posted:  Hello this is some other text   As an example, see an screenshot of the preview:    and a screenshot of the posted content, where the ---- becomes a &lt;hr&gt;:  Note a similar bug I also reported: . Convert UTC/GMT time to local time We are developing a C# application for a web-service client. This will run on Windows XP PC's.  One of the fields returned by the web service is a DateTime field. The server returns a field in GMT format i.e. with a "Z" at the end.  However, we found that .NET seems to do some kind of implicit conversion and the time was always 12 hours out.  The following code sample resolves this to some extent in that the 12 hour difference has gone but it makes no allowance for NZ daylight saving.  CultureInfo ci = new CultureInfo("en-NZ"); string date = "Web service date".ToString("R", ci); DateTime convertedDate = DateTime.Parse(date);               As per :     UTC/GMT Offset       Standard time zone: UTC/GMT +12 hours   Daylight saving time: +1 hour   Current time zone offset: UTC/GMT +13 hours     How do we adjust for the extra hour? Can this be done programmatically or is this some kind of setting on the PC's? Does a man contain all the genes needed to make a woman? This question is brought on by a Sci Fi novel I am thinking about writing. The plot device involves a colonist in charge of building a population on a new planet who loses his supply of embryos and so forth in the landing. With the artificial "wombs" intact, he populates the planet with clones of himself.  If he wanted to introduce enough variation (without making up new genes, only rearranging) in the population to allow them to be able to reproduce naturally without inbreeding problems, would he be able to? In particular, could he make a woman?  Alternately, could a woman (without a Y chromosome) do the the inverse?  At the risk of introducing bias into the answers, the plot as it stands assumes he is a male and he CAN'T do any of the above and he is restricted to clones. Compactness of  Multiplication Operator on $L^2$ How to "cat" or "less" a libreoffice writer .odt file? At work today, I came across the volatile keyword in Java. Not being very familiar with it, I found . Given the detail in which that article explains the keyword in question, do you ever use it or could you ever see a case in which you could use this keyword in the correct manner? Why is the direct product of a finite number of nilpotent groups nilpotent? C: pointer to struct in the struct definition How can I have a pointer to the next struct in the definition of this struct:  typedef struct A {   int a;   int b;   A*  next; } A;   this is how I first wrote it but it does not work. Is convex surface normal in cast iron skillet? I am new to cast iron skillet. I have cooked with it several times and found the Lodge 12" cast iron skillet has a convex surface which is not observable unless you pour oil on it.  When I cook, the oil move to rim of the skillet and makes the center short of oil. Is it normal?  EDIT: I added the photo of the stove and skillet for reference Can I delete unnecessary device simulators of Xcode? I found that Xcode on my laptop consumes much of its storage, so I am trying to delete unnecessary files in Xcode.  There are four directories under Application/Xcode.app/Contents/Developer/Platforms/. I feel that WatchSimulator.platform and AppleTVSimulator.platform are not necessary, because I use Xcode almost only for basic iOS development.  I would like to know if I can delete those platforms directories directly? Which manga chapter correspond to the end of episode 12 of season 2 of the anime?