3. Dates and Times

! -----------------------------
! All examples use the "calendar" vocabulary
USE: calendar

[ "Today is day " % now day-of-year # " of the current year." % ] "" make print
! Today is day 132 of the current year.
! -----------------------------

! -----------------------------
now ! puts timestamp on stack

! accessing day
day>>
! -----------------------------

! Formatting the date with "calender.format" vocabulary
USE: calendar.format

now timestamp>rfc3339
! Top of stack: "2008-05-11T22:39:01+02:00"

now timestamp>ymd
! Top of stack: "2008-05-11"
! -----------------------------

! -----------------------------
! Epoch milliseconds
now timestamp>millis
! Top of stack: 1210538827773

! Calculate seconds 
1000 / >integer
! -----------------------------

! GMT milliseconds
gmt timestamp>millis
! Top of Stack: 1210539018199

! -----------------------------
! Epoch milliseconds to timestamp
1210538827773 millis>timestamp

! -----------------------------
! Durations can be added and substracted with the words "time+" and "time-"
now 5 days time+ timestamp>ymd print
! 2008-05-17
now 5 days time- timestamp>ymd print
! 2008-05-07
! -----------------------------
1973 1 18 3 45 50 gmt-offset-duration <timestamp>   ! Birthtime
    0 0 55 2 17 5 <duration>                        ! Interval
    time+
    timestamp>string "Then is " swap append print
! Then is Wed, 14 Mar 1973 06:02:55
! -----------------------------
"Nat was 55 days old on: " 1973 1 18 <date> 55 days time+ timestamp>ymd append print
! Nat was 55 days old on: 1973-03-14
! -----------------------------

! -----------------------------
! Timestamps can be substracted from each other with "time-". You get a duration,
! which can be converted to the number of seconds, minutes, etc.
now 5 days time-        ! 5 days before
    now 5 days time+    ! in 5 days
    time-               ! substracting the two timestamps
    dt>days .           ! converting duration to number of days and prettyprinting it.
! -10
! -----------------------------
! Putting duration since lunar landing onto the stack:
now
    1969 7 20 20 17 40 instant <timestamp>   ! 1969-07-20 20:17:40 UTC
    time-
! -----------------------------
USING: calendar math.parser ;
1981 6 16 4 35 25 instant <timestamp>   ! 16 Jun 1981, 4:35:25 UTC, Bree
1973 1 18 3 45 50 instant <timestamp>   ! 18 Jan 1973, 3:45:50 UTC, Nat
time-
dt>seconds
dup     ! Duplicates top of stack so we can use it later again.

[ "There were " % # " seconds between Nat and Bree" % ] "" make print
! There were 265337375 seconds between Nat and Bree

[ dup 60 mod dup , ! seconds
  - 60 /  ! rest in minutes
  dup 60 mod dup , ! minutes
  - 60 /  ! rest in hours
  dup 24 mod dup , ! hours
  - 24 /  ! rest in days
  dup 7 mod dup , ! days
  - 7 / , ! weeks
] { } make

[ [ "(" % # " weeks, " % # " days, " % # ":" % # ":" % # ")" % ] "" make ] with-datastack
first print
! (438 weeks, 5 days, 0:49:35)

! -----------------------------
1981 6 16 <date>    ! 16 Jun 1981, Bree
1973 1 18 <date>    ! 18 Jan 1973, Nat
time-
dt>days
[ "There were " % # " days between Nat and Bree" % ] "" make print
! There were 3071 days between Nat and Bree
! -----------------------------