In the future:

hence ( duration -- timestamp )

In the past:

ago ( duration -- timestamp )

Invert a duration:

before ( duration -- -duration )

Days of the week relative to now:

sunday ( timestamp -- timestamp' )

monday ( timestamp -- timestamp' )

tuesday ( timestamp -- timestamp' )

wednesday ( timestamp -- timestamp' )

thursday ( timestamp -- timestamp' )

friday ( timestamp -- timestamp' )

saturday ( timestamp -- timestamp' )

New timestamps relative to calendar events:

start-of-year ( object -- timestamp )

start-of-month ( timestamp -- timestamp' )

start-of-week ( timestamp -- timestamp' )

midnight ( timestamp -- timestamp' )

noon ( timestamp -- timestamp' )