Honestly? Any time can work.
For instance you can have a whole week end focused on tantric sex with in depth exploration of your new skills...
Or you can have a morning quick energetic tantric session before you get up...
Or you can have a 15 min lunch tantric sex break.
Or have a whole evening dedicated to tantric pleasure.
All of these options do work, so need to limit yourself.
Now, I believe that amongst ALL these possible choices, the one that suits best our natural rhythms is evening 8-10pm.
You don't have to stretch your session for 2 hours of course. You can have for instance a 30 or 60 min tantric play session around that time of the evening.
If you want to develop your tantric sex skills, I believe that's the best time to practice.
A 2 hours space gives you plenty of time to dive into it.
The evening creates a refined and romantic energy.
Lower the lights, uses candles and incense.
You can really set it up like a daily tantric play meeting with your partner.