Adding one

The two-step wizard: the message, then when it shows

Add announcement opens a wizard in two steps. Message asks what it says:

Field	Meaning
Message	The text, at most 500 characters. Required.
Type	Its colour and icon: blue for Info (the default), amber for Warning, red for Danger

When asks when it shows:

Field	Meaning
Start date	It shows from this moment. Leave it empty to show it at once.
End date	At this moment it hides and is deleted. Leave it empty to keep it until you delete it.

The end date must come after the start date, and lie in the future.