So a few weeks ago someone had asked how to do some "How to validate a
date format in service
portal?"

So this came up in a chat I was having this week.

To use the g_user_date_format, g_user_date_time_format and
getDateFromFormat(), you would have to re-include the JS file that
declares these things.

To do that goto the widget where you get a failure message and add a new
dependency to a new UI script where you copy/paste the code from
https://hi.service-now.com/scripts/calendar.js.

Then all your old calls ought to work as described in other posts.

// returns a date object you can test against for date/time 
// variables/fields
new Date(getDateFromFormat(newValue, g_user_date_time_format));

// returns a date object you can test against for date 
// variables/fields
new Date(getDateFromFormat(newValue, g_user_date_format));