A business calendar defines business and non-business days. The significance of a day being a business day or a non-business day is user-determined. For example, a business day could be a work day, and a non-business day could be either a non-working day, a weekend day, a holiday, or a vacation day. You can define different week patterns (weekdays and weekends) and exceptions (holidays and business open and closed days) for the system-defined calendars.
All three calendars are based on the Gregorian calendar. The Gregorian calendar has 365 days in most years and 366 days in a leap year. The calendars differ in how they define weeks and whether they allow partial weeks. You can use macros to specify weekday/weekend patterns and exceptions to the patterns.
The calendars support January 1, 1900, to December 31, 2100. The default session calendar is Teradata. Each calendar defaults to all business days. You can change that pattern using a macro. See About Business Calendar Macros.