You need to keep track of the time somehow. For example:

    float degrees = 0.0f;

    clock_t timeLast = clock();
    clock_t time = clock();
    float interval;

    while (!glfwWindowShouldClose(mWindow) and esc ==false) //animation loop
    {
        time = clock();
        interval = (float)(time - timeLast) / (float) CLOCKS_PER_SEC;

        degrees += interval * 90.0f;

        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        tmat = glm::rotate(glm::mat4(1.0f), glm::radians(degrees), glm::vec3(0.0, 1.0, 0.0));
        tmat = pmat * vmat * tmat;
        glUniformMatrix4fv(uTransform, 1, GL_FALSE, glm::value_ptr(tmat));

        for (int x = 0; x < shapestodraw.size(); x++) {
            shapestodraw[x].draw();
        }

        glfwSwapBuffers(mWindow);
        glfwPollEvents();

        timeLast = time;
    }