Is there a way to create a stringstream from a string_view without copying data?

I think that's a pretty straighforward question. I'd specifically like to use std::get_time, but it requires some sort of a stream to be used with. I am passing the data in a string_view and would like to avoid copying it just to parse the date.

You can do that easily with Boost.Iostreams library:

#include <boost/iostreams/device/array.hpp>
#include <boost/iostreams/stream.hpp>

#include <iostream>
#include <string>

int main() {
    std::string_view buf{"hello\n"};
    boost::iostreams::stream<boost::iostreams::basic_array_source<char>> stream(buf.begin(), buf.size());

    std::string s;
    stream >> s;
    std::cout << s << '\n';
}

You should be able to do that with std::stringstream and std::basic_stringbuf<CharT,Traits,Allocator>::setbuf but the C++ standard botched its requirements:

The effect [of setbuf] is implementation-defined: some implementations do nothing, while some implementations clear the std::string member currently used as the buffer and begin using the user-supplied character array of size n, whose first element is pointed to by s, as the buffer and the input/output character sequence.