System.FormatException:String was not recognized as a valid date time |When I open a app

System.FormatException:String was not recognized as a valid date time.........
I tried to open an app and I got this error.I don't know anything about coding or C#.Please tell me the solutions in simple steps.I have just reinstalled my Windows 10 to a previous build 1511.I got this error before also when I made a new user account.It usually appeared at the start.But this error appears when I open an app known as Who's on my Wifi..I know there is no problem with that app for sure
Vedant NaikAsked:
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You could check your Date Time Format under the Region and language settings, but you will most likely have to contact Support for your application:
Vedant NaikAuthor Commented:
It doesn't appear now.It occured only at the first time

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Vedant NaikAuthor Commented:
I solved it on my own
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Windows 10

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