Server Validation for Time HH:MM M/PM format

case "time":

 {

                            //Regex regExpression = new Regex(@"^(\d{2}):(\d{2})\s{1}(([aA])|([pP]))[mM]$");

                            //new Regex(@"^(\d{2}):(\d{2})\s{1}([AP]M)$");

                            // ^(([1-9]{1})|([0-1][1-2])|(0[1-9])|([1][0-2])):([0-5][0-9])(([aA])|([pP]))[mM]$

                            Regex regExpression = new Regex(@"^(([1-9]{1})|([0-1][1-2])|(0[1-9])|([1][0-2])):([0-5][0-9])\s{1}(([aA])|([pP]))[mM]$");

                            if (drValidation["value"].ToString().Trim().Length > 0)

                                if(!regExpression.IsMatch(drValidation["value"].ToString().Trim()))

                                {

                                    strError.Append("");

                                    blnReturnVal = false;

                                }

                            break;

                        }