Can't copy nuget file into destination when I use MSBuild Property Functions

I have two goals on my current task; increment the version number of a Nuget package version automatically, and copy the generated .nupkg file into a new folder after the build.

With <GeneratePackageOnBuild>True</GeneratePackageOnBuild> inside my .csproj file I am trying to use a dynamic method (MSBuild Property Functions) to increase the version number of my assembly version. Instead of static definition <version>1.0.0</version> I am able to create something dynamic like this; <version>$([System.DateTime]::Now.ToString("yyyy.MM.dd"))</version>. This creates a file named projectName.2017.7.26.nupkg inside the bin/debug folder.

This process generates a file but it causes an synchronization issue in msbuild build process. On the second step, when I try to copy the file to the destination, I get the error: Could not copy the file "bin\Debug\projectName.2017.07.26.nupkg" because it was not found

Half a second after this error shows up, the Nuget package file appears in the bin\debug folder with the same name.

If I don't use $([System.DateTime]::Now.ToString("yyyy.MM.dd")) but use a static version number like 1.0.101, everything works fine and the file gets copied to the destination folder.

This is the relevant parts from my csproj file:

<PropertyGroup>
    <NewVersionNumber>$([System.DateTime]::Now.ToString("yyyy.MM.dd"))</NewVersionNumber>
    <CopyDestionationPath>..\Nuget</CopyDestionationPath>
</PropertyGroup>
<PropertyGroup>
    <TargetFrameworks>netcoreapp1.0;net46;net40</TargetFrameworks>
    <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
    <PackageId>$(AssemblyName)</PackageId>
    <version>$(NewVersionNumber)</version>
    <title>A Package</title>
    .....
</PropertyGroup>
.....
<Target Name="CopyPackage"  AfterTargets="Pack">
    <ItemGroup>
      <OldNugetFiles Include="$(CopyDestionationPath)\*nupkg" />
    </ItemGroup>
    <ItemGroup>
      <NewNugetFile Include="$(OutputPath)$(PackageId).$(PackageVersion).nupkg" />
    </ItemGroup>
    <Delete Files="@(OldNugetFiles)" />
    <Copy SourceFiles="@(NewNugetFile)" DestinationFolder="$(CopyDestionationPath)"/>
</Target>

Do I need something else in AfterTargets of CopyPackage task, currently it's set to pre-defined target of Pack?