Megha, my bad. I thought the u_end_time would return a String in hh:mm:ss format but it seems to be of type GlideDate.

In this case, .getTime() is returning a date/time in format "1970-01-01  hh:mm:ss". Since there is a date part (i.e "1970-01-01", the script was calculating the time incorrectly).

I've fixed the script to use <GlideDateTime>.add(<GlideTime>).

  var gdtCurrent = new GlideDateTime();  // set to current datetime (in UTC)
  var gdtStart =  new GlideDateTime(gs.beginningOfToday());  // initialize to today midnight
  var gdtEnd =  new GlideDateTime(gs.beginningOfToday());  // initialize to today midnight

  var gtStart = new GlideTime();
  gtStart.setValue(grHRAssociate.u_beginning_time.getDisplayValue());  // set GlideTime to start time value from the table
  gdtStart.add(gtStart);  // add GlideDate to current midnight date

  var gtEnd = new GlideTime();
  gtEnd.setValue(grHRAssociate.u_end_time.getDisplayValue());  // set GlideTime to end time value from the table
  gdtEnd.add(gtEnd);  // add GlideDate to current midnight date

  if (gdtCurrent.getNumericValue() >= gdtStart.getNumericValue() && gdtCurrent.getNumericValue() <= gdtEnd.getNumericValue()) {
    agents.push(grHRAssociate.u_hr_associate.toString());
  }

Tested the logic of the script using the following script.

var grHRAssociate= new GlideRecord('<user table>');
if (grHRAssociate.get('<sys_id of a record>')) {
  var gdtCurrent = new GlideDateTime();
  gdtCurrent.setDisplayValueInternal("<datetime in local timezone>");  // e.g. "2022-03-13 23:15:00"
  var gdtStart =  new GlideDateTime(gs.beginningOfToday());
  var gdtEnd =  new GlideDateTime(gs.beginningOfToday());
  gs.info("gdtStart:" + gdtStart.getDisplayValue() + " gdtEnd:" + gdtEnd.getDisplayValue() + " current:" + gdtCurrent.getDisplayValue());

  var gtStart = new GlideTime();
  gtStart.setValue(grHRAssociate.u_beginning_time.getDisplayValue());
  gdtStart.add(gtStart);

  var gtEnd = new GlideTime();
  gtEnd.setValue(grHRAssociate.u_end_time.getDisplayValue());
  gdtEnd.add(gtEnd);

  gs.info("start:" + gdtStart.getDisplayValue() + " end:" + gdtEnd.getDisplayValue() + " current:" + gdtCurrent.getDisplayValue());

  gs.info('numericValue(). gdtCurrent :' + gdtCurrent .getNumericValue() + ' gdtStart:' + gdtStart.getNumericValue() + ' gdtEnd:' + gdtEnd.getNumericValue());

  if (gdtCurrent.getNumericValue() >= gdtStart.getNumericValue() && gdtCurrent.getNumericValue() <= gdtEnd.getNumericValue()) {
    //agents.push(grHRAssociate.u_hr_associate.toString());
    gs.info("OK");
  } else {
    gs.info("NG");
  }
}

Sample execution result. beginning time:9:00, end time:23:30, current time:23:15 -> OK

*** Script: gdtStart:2022-03-13 00:00:00 gdtEnd:2022-03-13 00:00:00 current:2022-03-13 23:15:00
*** Script: start:2022-03-13 09:00:00 end:2022-03-13 23:30:00 current:2022-03-13 23:15:00
*** Script: numericValue(). gdtCurrent :1647180900000 gdtStart:1647129600000 gdtEnd:1647181800000
*** Script: OK