Interesting that there is another tool[1] on Show HN right now that does this but for strftime instead of moment.js, I guess I need to build one for Golang's weird time formatting.
I made a similar tool that could take almost arbitrery text strings like “mar 27, ’09” or “07/08/97” and generate a list of all valid interpretations. Eg. “07/08/97” would generate [{d: 7, m: 8, y: 97}, {d: 8, m: 7, y: 97}], but not any where 97 is a day or month, since that wouldn’t be a valid date.
It's to remove ambiguity (not all), i.e. you select a date and then specify how you want it to look. For example, the date 12/05/2017 can be interpreted as either DD/MM/YYYY or MM/DD/YYYY but if you select a date first and then describe your desired format we can exclude one of the possibilities.
Perhaps consider removing the choice? For example, have only one input (the desired format) and above it some text saying "How would you format '28/03/2018 21:37'?".
This removes the confusion of two inputs, and provided you select an unambiguous baseline date (day & hour > 12) it should be more clear.
just a suggestion but can we get a bit more than one page with a couple of fields ?
It's okay to get straight to the point and being minimalistic but a few infos about the author and whether there is a github repo for the code... those things would help