| Known child units | 
| 
 Exceptions
| Date_Error |  | 
  Any calendar operation may raise this exception if a date is not valid
  for a particular calendar. Possible reasons for Date_Errorbeing
  raised include: passing a date before 15-OCT-1582 to a Gregorian
  calendar, or passing a non-existing date to a Universal calendar, such
  as a date in the range 05-OCT-1582 to 14-OCT-1582, if the switch date
  of the Universal calendar is not changed. |  | 
| 
 Type Summary | 
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 Other Items: | 
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| type Calendar is abstract tagged null record;
 |  | 
  Abstract root type for all calendars. Note: any other operations are
  added by derived types. For instance, operations on days and months
  are added in child package  
  Util.Calendars.Western.
 
  They're not added here because other calendar systems may not have
  a concept of months in the sense of the western calendars.
 |  
 | 
| 
| subtype Year_Number is Integer;
 |  | 
  But any calendar has a concept of a year! (Even if the counting systems
  may differ wildly, as may the length of a year.)
 |  
 | 
| 
| function Year
  (Base : in Calendar;
   Date : in Util.Times.Time)
  return Year_Number
  is abstract;
 |  | 
  Return the year of the Date. May raiseDate_Errorif theDateis
  not a valid date for the given calendarBase. |  
 | 
| 
| function Image
  (Base : in Calendar;
   Date : in Util.Times.Time)
  return String
   is abstract;
 |  | 
  Returns a string representation of the given Date. May raiseDate_Errorif theDateis not a valid date for the given calendarBase. |  |