Here’s a bookmarklet for for the web, for use when scheduling posts. If you click the bookmarklet when you schedule a post (but before you click into the date field) you’ll have a date filled out that you can then modify as needed (to, say, add a couple hours to the time, or adjust the day while leaving the rest of the values alone).

javascript: (() => { const datePicker = document.querySelector("#input_date"); const curDate = datePicker.getAttribute("placeholder"); datePicker.setAttribute("value", curDate); datePicker.setAttribute("onclick", null); })();

Tested quickly in Firefox. It takes the date from the “placeholder” text, moves it to the “value” text, and then removes the handler that clears the date when you click into the field.

I have a previous bookmarklet for here.