Facebook Messenger does not provide good options for selecting time. Entering time information via text is slow, error prone and clunky, and also requires a lot of validation. A better way would be to use a time picker interface similar to time pickers in Android and iOS native.
The intended use case of this form is for a user to open this page as a webview to select time. After time selection, the page will make a HTTP request to your endpoint of choice to update the state of the user. This ought to then be followed up with some validation message to the user.
Credits to ecmadao for doing the heavy lifting of making the best time picking component I could find.