Any reason why you need it sent to a specific time? Is the time arbitrary? Or, is there a specific option like you can choose from 3 times in a day, say 8am, 12nn or 6pm.
If it is random, I’m not sure if it can be done without polling which may be process intensive. Which means in a day the program will check all records around 86400 times assuming your time is rounded to second, and around 1440 times if rounded to minute.
In any case, I think this one needs to be programmed in an app.