DateTime Related Functions

string a = "to_date('" + dtpStart.Value.ToString("yyyy/MM/dd") + "', 'yyyy/mm/dd')";
            string b = "to_date('" + dtpEnd.Value.ToString("yyyy/MM/dd ") + "23:59:59', 'yyyy/mm/dd hh24:mi:ss')";
            gDtNursingIndexMasterResult = getTableData.getTableData("select * from NURSING_INDEX_CHECK_MASTER where CHECK_DATE Between " + a + " and " + b + "");
            gDtNursingIndexMasterResult.Tables[0].TableName = "NURSING_INDEX_CHECK_MASTER";
            gDtNursingIndexDetailResult = getTableData.getTableData("select * from NURSING_INDEX_CHECK_DETAIL where CHECK_DATE Between " + a + " and " + b + "");
            gDtNursingIndexDetailResult.Tables[0].TableName = "NURSING_INDEX_CHECK_DETAIL";

The Oracle/PLSQL TO_DATE function converts a string to a date.

TO_DATE( string1, [ format_mask ], [ nls_language ] )

Parameters or Arguments

string1 is the string that will be converted to a date.

format_mask is optional. This is the format that will be used to convert string1 to a date.

nls_language is optional. This is the nls language used to convert string1 to a date.

TO_DATE('2003/07/09', 'yyyy/mm/dd')	would return a date value of July 9, 2003
TO_DATE('070903', 'MMDDYY')	would return a date value of July 9, 2003
TO_DATE('20020315', 'yyyymmdd')	would return a date value of Mar 15, 2002

String.Format("{0:d/M/yyyy HH:mm:ss}", dt); // "9/3/2008 16:05:07" - english (en-US)

String.Format("{0:t}", dt);  // "4:05 PM"                         ShortTime
String.Format("{0:d}", dt);  // "3/9/2008"                        ShortDate
String.Format("{0:T}", dt);  // "4:05:07 PM"                      LongTime
String.Format("{0:D}", dt);  // "Sunday, March 09, 2008"          LongDate
String.Format("{0:f}", dt);  // "Sunday, March 09, 2008 4:05 PM"  LongDate+ShortTime
String.Format("{0:F}", dt);  // "Sunday, March 09, 2008 4:05:07 PM" FullDateTime
String.Format("{0:g}", dt);  // "3/9/2008 4:05 PM" ShortDate+ShortTime
String.Format("{0:G}", dt);  // "3/9/2008 4:05:07 PM"             ShortDate+LongTime
String.Format("{0:m}", dt);  // "March 09"                        MonthDay
String.Format("{0:y}", dt);  // "March, 2008"                     YearMonth
String.Format("{0:r}", dt);  // "Sun, 09 Mar 2008 16:05:07 GMT"   RFC1123
String.Format("{0:s}", dt);  // "2008-03-09T16:05:07"             SortableDateTime
String.Format("{0:u}", dt);  // "2008-03-09 16:05:07Z"            UniversalSortableDateTime

http://msdn.microsoft.com/en-us/library/26etazsy(v=vs.110).aspx