I'm fairly sure I have interpreted this right, I think that you set the time at the beginning of the run so that you get the first massage just before the ds thinks it's midnight. Then after beatimg grant it's the next day so you can get a second massage. Is this correct, or is there another element to it? Because I did exactly this and it did not let me get the second massage.

That's all there is to it. Maybe you got the first massage after the day rolled over?

Exactly. Note that not getting the second massage is not the end of the world. You can still progress the run and get lucky. The current top time on the leaderboards actually does not even try to get two massages at all.

Also, if you are certain you did it right: if you actively waited for the time to roll over midnight inside of the massage lady's house, she will still tell you to come back. You need to leave and re-enter the house. That is why - if I happen to wait - will wait outside the house.

Thanks wartab, I actually have gotten lucky like this before, but as I can currently improve on many other things to lower my time, I would prefer to get both the massages to avoid wasting time riding around in coumarine city if it doesn't come off.
May it have something to with changing the time during the run? My time up until cyllage was quite slow, and i had had about 15 encounters without hawlucha, so I saved and went and changed the time so that I could get both massages, (obviously for practice, as I had already given up on the run). Would this effect things, does the game stick with the original time when you start the game? Otherwise I'll try what wartab suggested, if that doesn't work, I must've just gotten the first massage too late.

I'm pretty sure that is the reason it did not work. I'm unsure about X/Y, but changing the clock has messed with clock based events in previous gens before.

ok thanks, I'll try both.