A cheat sheet for working with the ServiceNow Date and Date/Time fields on the client side.

servicenow_date_field_typecasting.js

// Display value
var dateStr = g_form.getValue('<date_field_name>');

// Display value => milliseconds
var ms = getDateFromFormat(dateStr, g_user_date_format);

// Milliseconds => JS Date instance
var date = new Date(ms);

// JS Date instance => display value
formatDate(date, g_user_date_format) === dateStr; // true

servicenow_date_time_field_typecasting.js

// Display value
var dateTimeStr = g_form.getValue('<date_time_field_name>');

// Display value => milliseconds
var ms = getDateFromFormat(dateTimeStr, g_user_date_time_format);

// Milliseconds => JS Date instance
var date = new Date(ms);

// JS Date instance => display value
formatDate(date, g_user_date_time_format) === dateTimeStr; // true