Any text boxes in the app which ask for a date or time support a number of different formats.
Dates and times can be combined together - the safest way is usually to write date at time to avoid any ambiguity, e.g.: Jun 23 at 5pm.
Dates and times will always assumed to be in the future, unless explicitly stated otherwise. For example, if today's date is July 15th, and you set a step as being due on July 5th, the app will assume you mean July 5th next year, unless you explicitly write the year along with the date.
Some examples of supported formats are listed below: