Built-in Constants

VBA.vbDateTimeFormat

vbGeneralDate (0) 
vbLongDate (1) 
vbShortDate (2) 
vbLongTime (3) 
vbShortTime (4) 

This enumeration is used with the FORMATDATETIME

VBA.vbDayOfWeek

vbUseSystemDayOfWeek (0) 
vbSunday (1) 
vbMonday (2) 
vbTuesday (3) 
vbWednesday (4) 
vbThursday (5) 
vbFriday (6) 
vbSaturday (7) 

This enumeration is used with the DATEDIFF, DATEPART, FORMAT, WEEKDAY and WEEKDAYNAME

VBA.vbFirstWeekOfYear

vbUseSystem (0)       'The week specified in your system settings  
vbFirstJan1 (1)       'The week in which January 1 occurs  
vbFirstFourDays (2)   'The first week that has at least four days in the new year  
vbFirstFullWeek (3)   'The first full week of the year  

This enumeration is used with the DATEDIFF, DATEPART and FORMAT

VBA.Calendar

There is a property that can be used to change the calendar type.

VBA.Calendar = vbCalGreg    'this is the default  
VBA.Calendar = vbCalHijri