Update date input to recommend accepting month names

[frankieroberto]

Back in May 2022, we discovered that hundreds of users were inputting months using full or abbreviated month names in the ‘Apply for teacher training’ service – see full table of inputs.

We made a change to accept these as valid months which dramatically reduced the number of errors. This change was also later made in another service, ‘Find a lost TRN’.

Given this data and the comments in the backlog thread about people with dyscalculia finding it harder to convert month names into numbers (although possibly most users need at least a second or so to think about this?), it feels like it’s worth adding to the general guidance?

One unresolved open question is about whether this should be advertised, or just be a hidden feature? Arguably the hint text could say something like "For example, 31 8 2005 or 31 aug 2005" to make it clear that both forms are accepted (and avoid people having to do the conversion in their head unnecessarily) but perhaps this just adds confusion?