Is your feature request related to a problem or area of OpenRefine? Please describe.
Say you want to manually edit a cell to input a date there. This is what it currently looks like:

The problems are:
- As a user, how do I know which formats are supported? Especially if I start with a text value and want to transform it to a date, I should not have to refer to the user manual to find out how to format it.
- When I try to input a wrong date, a JS alert pops up: "Not a valid date." That is not very helpful!
Describe the solution you'd like
Find a way to add a short description of the supported format(s) to the dialog itself, and/or improve the error message to mention the formats.
Describe alternatives you've considered
We could consider using an off-the-shelf date picker but it is not clear to me whether that would be really more user-friendly in a data cleaning context. Perhaps it could be used optionally, with still the ability to modify the date textually?
Additional context
Brought up in a documentation meeting with @allanaaa and @thadguidry.
Is your feature request related to a problem or area of OpenRefine? Please describe.
Say you want to manually edit a cell to input a date there. This is what it currently looks like:

The problems are:
Describe the solution you'd like
Find a way to add a short description of the supported format(s) to the dialog itself, and/or improve the error message to mention the formats.
Describe alternatives you've considered
We could consider using an off-the-shelf date picker but it is not clear to me whether that would be really more user-friendly in a data cleaning context. Perhaps it could be used optionally, with still the ability to modify the date textually?
Additional context
Brought up in a documentation meeting with @allanaaa and @thadguidry.