I got the sense that it took a few days to a few weeks for the First Order to marshal their various ships for an attack on the Resistance base. The days, or probably weeks, gives Finn time to wake from his coma, Rey to travel to Achtoo and for the Resistance to abandon their base. From that point it seems at most to be a a few days that the Resistance fleet jumps to hyperspace, realize they're being tracked, then make the sublight journey to Krait. Holdo keeps mentioning only X number of hours of fuel remaining, so the sublight chase wasn't very long. It's at this point that Rey returns with Chewie.
I'm going to say a month max between the end of TFA and TLJ.