I can see it for other clan members by doing a guard payoff but for my own town all I get is the frustrating "3w 1d" format which can be anytime in a 24hr period. If there isn't a command to do this, there should be.
I am not sure why you would need to do this as it is a long way off and the timing would become clearer then.
You could perhaps ask a clan member to gpo you, but I'm am guessing it might just give you the same answer of "3w 1d" .
IF you really need to know exactly just make a note when next applying nearer its expiration.
Make the peace treaty which you use most often a "favourite" and that allows you to see the number of days and hours remaining on your shield by clicking on "Boosts".
I commend the practice of maintaining a shield of a few days or a week at all times. The game is generous (currently at any rate) with 8 hour peace treaty items and you can use many of these every day without running any risk of running out. Letting a shield run down to just minutes left is an unnecessary risk.
