Oracle Date Calculations


Oracle Date

The DATE datatype returns as number a decimal value representing the number of day.
Oracle can store dates in the Julian era, ranging from January 1, 4712 BCE through December 31, 4712 CE (Common Era, or 'AD'). Unless BCE ('BC' in the format mask) is specifically used, CE date entries are the default.

Decimal date Arithmetic

Since the DATE datatype returns as number a decimal value representing the number of day you can do some simple date arithmetic by adding a decimal number.

 select sysdate + 1  from dual;

 select trunc(sysdate - 90)  from dual;

 select sysdate + 1/24*4  from dual;

Date Conversion functions to_date and to_char

  to_date('Date String', 'Format String')
  to_date('20122003 23:12:14', 'DDMMYYYY HH24:MI:SS)

  'StartDate:' || to_char(start_date, 'DDMMYYYY HH24:MI:SS)

Format Strings

 YEAR 		Year, spelled out 
 YYYY 		4-digit year 
 Y 		Last 3, 2, or 1 digit(s) of year. 
 I 		Last 3, 2, or 1 digit(s) of ISO year. 
 IYYY 		4-digit year based on the ISO standard 
 RRRR 		Accepts a 2-digit year and returns a 4-digit year.
 A 		value between 0-49 will return a 20xx year.
 A 		value between 50-99 will return a 19xx year. 
 Q 		Quarter of year (1, 2, 3, 4; JAN-MAR = 1). 
 MM 		Month (01-12; JAN = 01). 
 MON 		Abbreviated name of month. 
 MONTH 		Name of month, padded with blanks to length of 9 characters. 
 RM 		Roman numeral month (I-XII; JAN = I). 
 WW 		Week of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year. 
 W 		Week of month (1-5) where week 1 starts on the first day of the month and ends on the seventh. 
 IW 		Week of year (1-52 or 1-53) based on the ISO standard. 
 D 		Day of week (1-7). 
 DAY 		Name of day. 
 DD 		Day of month (1-31). 
 DDD 		Day of year (1-366). 
 DY 		Abbreviated name of day. 
 J 		Julian day; the number of days since January 1, 4712 BC. 
 HH 		Hour of day (1-12). 
 HH12 		Hour of day (1-12). 
 HH24 		Hour of day (0-23). 
 MI 		Minute (0-59). 
 SS 		Second (0-59). 
 SSSSS 		Seconds past midnight (0-86399). 
 FF 		Fractional seconds. Use a value from 1 to 9 after FF to indicate the number of digits in the fractional seconds. For example, 'FF4'. 
 AM, 		A.M., PM, or P.M. Meridian indicator 
 AD 		or A.D AD indicator 
 BC 		or B.C. BC indicator 
 TZD 		Daylight savings information. For example, 'PST' 
 TZH 		Time zone hour. 
 TZM 		Time zone minute. 
 TZR 		Time zone region. 

Month Calculations

Oracle uses the functions add_month the calculate proper dates including the end of month problematic:

   SELECT add_months(TO_DATE('29-JAN-2013'), 1) FROM DUAL;

   SELECT add_months(TO_DATE('29-JAN-2016'), 1) FROM DUAL;

   SELECT add_months(TO_DATE('28-FEB-2013'), 36) FROM DUAL;

Status: Published Date: 2017/06/05 14:14:14 Revision: 1.1

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