Phase portraits for non-autonomous ODE system

I understand how to use quiver function to plot phase portraits for autonomous systems of ordinary differential equations but a bit stuck with non-autonomous case. In particular how can i plot phase portraits for system like this?

Thanks in advance.

[Barend Braakbal]

If you have an autonomous system of equations you can calculate the critical points in the phase plane by putting the right side of the system of equations equal to 0. You will then get certain fixed coordinates for those critical points.

Now, if you have a non-autonomous system (like in your question) and you put the right hand side equal to 0 to calculate the critical points, then you will not get fixed coordinates,but instead, the location of those critical points will depend on t. If you want to visualize this, think about a two dimensional phase plane, with a t- axis perpendicular to the phase plane. Hope this helps you a bit.