Error Checking Between Two Dates

Is it possible to error check in a Lovelace UI?

I’ve set up two input.datetime helpers that are being used to identify the start and end date of a vacation period. Users select the desired dates, start and finish, from an entities card on a Lovelace panel. In turn these dates are used to changes how various entities in the house function.

I foresee a situation where a user could input a start date that is later than an end date. Or vise versa. Is there anything I can do from a coding perspective to alert users to this type of error and to ensure the end date of the selected vacation period is always later than the selected start date?

you could set up an automation to trigger an alert or notification depending on the values of the datetimes.

or use a conditional markdown card that pops up depending on the state of a binary sensor tht checks that one date is later than the other.

These are two great ideas! Never though about using a conditional markdown card. I give these a try over the weekend.

Thank you