I found that momentJS lowercase all strings. You can try on your browser
moment().format("dddd D MMMM YYYY HH:mm")
Or whatever format and that will set all datetime inputs to lower case.
The datetime parser on lib/rails_admin/support/datetime.rb method delocalize asumes all words are titleized. So when that method is called by parse_string it will return the same string, not having delocalized anything so when the DateTime.strptime is called it will receive a string in spanish or whatever and raise ArgumentError returning nil.
I fixed it by editing lib/rails_admin/support/datetime.rb delocalize method adding the titleize method.

How should i proceed?
** update **
To avoid having to maintain my own fork of rails admin i just added a js file on the edit action that changes moment to use custom Titleized translations
moment.updateLocale('es', {
weekdays: 'Domingo_Lunes_Martes_Miércoles_Jueves_Viernes_Sábado'.split('_'),
months : 'Enero_Febrero_Marzo_Abril_Mayo_Junio_Julio_Agosto_Septiembre_Octubre_Noviembre_Diciembre'.split('_'),
});
I found that momentJS lowercase all strings. You can try on your browser
Or whatever format and that will set all datetime inputs to lower case.
The datetime parser on
lib/rails_admin/support/datetime.rbmethod delocalize asumes all words are titleized. So when that method is called by parse_string it will return the same string, not having delocalized anything so when the DateTime.strptime is called it will receive a string in spanish or whatever and raise ArgumentError returning nil.I fixed it by editing lib/rails_admin/support/datetime.rb

delocalizemethod adding the titleize method.How should i proceed?
** update **
To avoid having to maintain my own fork of rails admin i just added a js file on the edit action that changes moment to use custom Titleized translations