The Halogen.HTML.Element.input function only allows a min property of type Number:
type HTMLinput = Interactive
( ...
, max :: Number
, min :: Number
...
)
However, for inputs with type=month, min and max take the form of a string with format YYYY-MM: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/input/month#min
The same issue applies to other input types, listed here: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Attributes/min#syntax