About Calendar Formats

Oracle Database stores this calendar information for each territory:

• First day of the week

  Sunday in some cultures, Monday in others. Set by the NLS_TERRITORY parameter.

• First week of the calendar year

  Some countries use week numbers for scheduling, planning, and bookkeeping. In the ISO standard, this week number can differ from the week number of the calendar year. For example, 1st Jan 2005 is in ISO week number 53 of 2004. An ISO week starts on Monday and ends on Sunday. To support the ISO standard, Oracle Database provides the IW date format element, which returns the ISO week number. The first calendar week of the year is set by the NLS_TERRITORY parameter.

• Number of days and months in a year

  Oracle Database supports six calendar systems in addition to the Gregorian calendar, which is the default. These additional calendar systems are:

  • Japanese Imperial

    Has the same number of months and days as the Gregorian calendar, but the year starts with the beginning of each Imperial Era.

  • ROC Official

    Has the same number of months and days as the Gregorian calendar, but the year starts with the founding of the Republic of China.

  • Persian

    The first six months have 31 days each, the next five months have 30 days each, and the last month has either 29 days or (in leap year) 30 days.

  • Thai Buddha uses a Buddhist calendar.

  • Arabic Hijrah has 12 months and 354 or 355 days.

  • English Hijrah has 12 months and 354 or 355 days.

  The calendar system is specified by the NLS_CALENDAR parameter.

• First year of era

  The Islamic calendar starts from the year of the Hegira. The Japanese Imperial calendar starts from the beginning of an Emperor's reign (for example, 1998 is the tenth year of the Heisei era).