A RelativeDateShortcut is a special string that represents a shortcut to a date phrase that can  be automatically mapped
 to a 
RelativeDateString for use in widgets that  leverage relative-dates, such as the
 
RelativeDateItem. 
 Note that some shortcuts indicate a time period
 but do not directly indicate whether the value refers to the start or end of the time period in question. This ambiguity
 can be resolved by specifying an explicit RelativeDateRangePosition when calling APIs
 that  convert from RelativeDates to absolute date values. This is the case for $today,  $tomorrow,
 $yesterday, $weekAgo, $weekFromNow, $monthAgo and $monthFromNow. If a range position
 is not explicitly passed, these will all default to the start of the day in question. 
 Builtin options include 
 -  $now - this moment 
-  $today - the current day. By default this resolves to the start of the current day
 though   an explicit RelativeDateRangePositionmay be used to specify the end of the
 current day.
-  $startOfToday - the start of today
-  $endOfToday - the end of today (one millisecond
 before the $startOfTomorrow) 
-  $yesterday - the previous day.
-  $startOfYesterday - the start of
 yesterday
-  $endOfYesterday - the end of yesterday (one millisecond before the $startOfToday) 
- 
 $tomorrow - the following day
-  $startOfTomorrow - the start of tomorrow 
-  $endOfTomorrow - the end of
 tomorrow 
-  $weekAgo - the current day of the previous week 
-  $weekFromNow - the current day of the
 next week 
-  $startOfWeek - the start of the current week 
-  $endOfWeek - the end of the current week
 
-  $monthAgo - the current day of the previous month 
-  $monthFromNow - the current day of the following
 month 
-  $startOfMonth - the start of the current month 
-  $endOfMonth - the end of the current month
 
-  $startOfYear - the start of the current year 
-  $endOfYear - the end of the current year