@niveditakumari,
Could you validate current.u_hr_hire_date has proper date value? Because your script working fine and calculating year difference in background with test value.
var hiringDate = '2015-10-06'; // (yyyy-MM-dd)
var hiringDateGd = new GlideDate();
hiringDateGd.setValue(hiringDate);
var currentDateGd = new GlideDate();
var hiringYear = hiringDateGd.getYearNoTZ();
var currentYear = currentDateGd.getYearNoTZ();
var experience = currentYear - hiringYear;
gs.info('Experience: ' + experience + ' years');
Best,
Rampriya S
