urbit/docs/pub/doc/hoon/library/3bc.md

section 3bC, Gregorian UTC

++dawn

Weekday of Jan 1

++  dawn                                                ::  weekday of jan 1
  |=  yer=@ud
  =+  yet=(sub yer 1)
  %-  mod  :_  7
  :(add 1 (mul 5 (mod yet 4)) (mul 4 (mod yet 100)) (mul 6 (mod yet 400)))
::

Computes which day of the week January 1st falls on for a year yer, producing an atom. Weeks are zero-indexed beginning on Sunday.

yer is an unsigned decimal, @ud.

~zod/try=> (dawn 2.015)
4
~zod/try=> (dawn 1)
1
~zod/try=> (dawn 0)
! subtract-underflow
! exit

---

++daws

Weekday of date

++  daws                                                ::  weekday of date
  |=  yed=date
  %-  mod  :_  7
  (add (dawn y.yed) (sub (yawn [y.yed m.yed d.t.yed]) (yawn y.yed 1 1)))
::

Produces the day of the week of a given date yed as an atom. Weeks are zero-indexed beginning on Sunday.

yed is a date.

~zod/try=> (daws [[a=%.y y=2.014] m=6 t=[d=6 h=21 m=9 s=15 f=~[0xa16]]])
5
~zod/try=> (daws (yore -<-))
2

(second example always returns the current date).

---

++deal

Add leap seconds

++  deal                                                ::  to leap sec time
  |=  yer=@da
  =+  n=0
  =+  yud=(yore yer)
  |-  ^-  date
  ?:  (gte yer (add (snag n lef:yu) ~s1))
    (yore (year yud(s.t (add n s.t.yud))))
  ?:  &((gte yer (snag n lef:yu)) (lth yer (add (snag n lef:yu) ~s1)))
    yud(s.t (add +(n) s.t.yud))
  ?:  =(+(n) (lent lef:yu))
    (yore (year yud(s.t (add +(n) s.t.yud))))
  $(n +(n))
::

Produces a date with the 25 leap seconds added.

yer is an absolute date, @da.

~zod/try=> (yore (bex 127))
[[a=%.y y=226] m=12 t=[d=5 h=15 m=30 s=8 f=~]]
~zod/try=> (deal `@da`(bex 127))
[[a=%.y y=226] m=12 t=[d=5 h=15 m=30 s=33 f=~]]
~zod/try=> (yore (bex 126))
[[a=%.n y=146.138.512.088] m=6 t=[d=19 h=7 m=45 s=4 f=~]]

---

++lead

Subtract leap seconds

++  lead                                                ::  from leap sec time
  |=  ley=date
  =+  ler=(year ley)
  =+  n=0
  |-  ^-  @da
  =+  led=(sub ler (mul n ~s1))
  ?:  (gte ler (add (snag n les:yu) ~s1))
    led
  ?:  &((gte ler (snag n les:yu)) (lth ler (add (snag n les:yu) ~s1)))
    ?:  =(s.t.ley 60)
      (sub led ~s1)
    led
  ?:  =(+(n) (lent les:yu))
    (sub led ~s1)
  $(n +(n))
::

Produces an absolute date (@ud) with the 25 leap seconds subtracted.

ley is a date.

~zod/try=> (yore `@da`(bex 127))
[[a=%.y y=226] m=12 t=[d=5 h=15 m=30 s=8 f=~]]
~zod/try=> (lead (yore `@da`(bex 127)))
~226.12.5..15.29.43
~zod/try=> (lead (yore `@da`(bex 126)))
~146138512088-.6.19..07.44.39

---

++dust

Print UTC format

++  dust                                                ::  print UTC format
  |=  yed=date
  ^-  tape
  =+  wey=(daws yed)
  ;:  weld
      `tape`(snag wey (turn wik:yu |=(a=tape (scag 3 a))))
      ", "  ~(rud at d.t.yed)  " "
      `tape`(snag (dec m.yed) (turn mon:yu |=(a=tape (scag 3 a))))
      " "  (scag 1 ~(rud at y.yed))  (slag 2 ~(rud at y.yed))  " "
      ~(rud at h.t.yed)  ":"  ~(rud at m.t.yed)  ":"  ~(rud at s.t.yed)
      " "  "+0000"
  ==
::

Produces a tape of the date in UTC format.

yed is a date.

~zod/try=> (dust (yore -<-))
"Tue, 21 Oct 2014 21:35:12 +0000"
~zod/try=> (dust [[a=%.y y=2.002] m=10 t=[d=11 h=12 m=20 s=55 f=~]])
"Fri, 11 Oct 2002 12:20:55 +0000"

---

++stud

Parse UTC format

++  stud                                                ::  parse UTC format
  |=  cud=tape
  ^-  (unit date)
  =-  ?~  tud  ~ 
      `[[%.y &3.u.tud] &2.u.tud &1.u.tud &4.u.tud &5.u.tud &6.u.tud ~]
  ^=  tud
  %+  rust  cud
  ;~  plug
    ;~(pfix (stun [5 5] next) dim:ag)
  ::
    %+  cook
      |=  a=tape
      =+  b=0
      |-  ^-  @
      ?:  =(a (snag b (turn mon:yu |=(a=tape (scag 3 a)))))
          +(b)
      $(b +(b))
    (ifix [ace ace] (star alf))
  ::
    ;~(sfix dim:ag ace)  
    ;~(sfix dim:ag col)
    ;~(sfix dim:ag col)  
    dim:ag  
    (cold ~ (star next))
  ==
::

Accepts a tape containing a date in UTC format and produces the unit of a date.

~zod/try=> (stud "Tue, 21 Oct 2014 21:21:55 +0000")
[~ [[a=%.y y=2.014] m=10 t=[d=21 h=21 m=21 s=55 f=~]]]
~zod/try=> (stud "Wed, 11 Oct 2002 12:20:55 +0000")
[~ [[a=%.y y=2.002] m=10 t=[d=11 h=12 m=20 s=55 f=~]]]
~zod/try=> (stud "Wed, 11 Oct 2002")
~

---

++unt

UGT to UTC time

++  unt                                                 ::  UGT to UTC time
  |=  a=@da
  (div (sub a ~1970.1.1) (bex 64))
::

~zod/try=/hom> (unt -<-)
1.413.927.704
~zod/try=> (unt ~20014.1.1)
569.413.670.400
~zod/try=> (unt ~2014.1.1)
1.388.534.400

Transforms Urbit Galactic Time to UTC time, producing an atom.

a is an atom.

---

++yu

UTC format constants

++  yu                                                  ::  UTC format constants
  |%

~zod/try=/hom> yu
<4.pgn 250.tmw 41.cmo 414.rvm 101.jzo 1.ypj %164>

---

++mon

Months

  ++  mon  ^-  (list tape)
    :~  "January"  "February"  "March"  "April"  "May"  "June"  "July"
        "August"  "September"  "October"  "November"  "December"
    ==
  ::

Produces a list of tapes containing the 12 months of the year.

~zod/try=/hom> mon:yu
<<
  "January"
  "February"
  "March"
  "April"
  "May"
  "June"
  "July"
  "August"
  "September"
  "October"
  "November"
  "December"
>>
~zod/try=/hom> (snag 1 mon:yu)
"February"

---

++wik

Weeks

  ++  wik  ^-  (list tape)
    :~  "Sunday"  "Monday"  "Tuesday"  "Wednesday"  "Thursday"
        "Friday"  "Saturday"
    ==
  ::

Produces a list of tapes containing the 7 days of the week, beginning with Sunday.

~zod/try=/hom> wik:yu
<<"Sunday" "Monday" "Tuesday" "Wednesday" "Thursday" "Friday" "Saturday">>
~zod/try=/hom> (snag 2 wik:yu)
"Tuesday"
~zod/try=/hom> (snag (daws (yore -<-)) wik:yu)
"Tuesday"

---

++les

Leap second dates

  ++  les  ^-  (list ,@da)
    :~  ~2012.7.1  ~2009.1.1  ~2006.1.1  ~1999.1.1  ~1997.7.1  ~1996.1.1
        ~1994.7.1  ~1993.7.1  ~1992.7.1  ~1991.1.1  ~1990.1.1  ~1988.1.1
        ~1985.7.1  ~1983.7.1  ~1982.7.1  ~1981.7.1  ~1980.1.1  ~1979.1.1
        ~1978.1.1  ~1977.1.1  ~1976.1.1  ~1975.1.1  ~1974.1.1  ~1973.1.1
        ~1972.7.1
    ==

Produces a list of the (absolute) dates ([@da]) of the 25 leap seconds

~zod/try=/hom> les:yu
~[
  ~2012.7.1
  ~2009.1.1
  ~2006.1.1
  ~1999.1.1
  ~1997.7.1
  ~1996.1.1
  ~1994.7.1
  ~1993.7.1
  ~1992.7.1
  ~1991.1.1
  ~1990.1.1
  ~1988.1.1
  ~1985.7.1
  ~1983.7.1
  ~1982.7.1
  ~1981.7.1
  ~1980.1.1
  ~1979.1.1
  ~1978.1.1
  ~1977.1.1
  ~1976.1.1
  ~1975.1.1
  ~1974.1.1
  ~1973.1.1
  ~1972.7.1
]
~zod/try=/hom> (snag 2 les:yu)
~2006.1.1

---

++lef

Back-shifted leap second dates

  ++  lef  ^-  (list ,@da)
    :~  ~2012.6.30..23.59.59   ~2008.12.31..23.59.58
        ~2005.12.31..23.59.57  ~1998.12.31..23.59.56
        ~1997.6.30..23.59.55   ~1995.12.31..23.59.54
        ~1994.6.30..23.59.53   ~1993.6.30..23.59.52
        ~1992.6.30..23.59.51   ~1990.12.31..23.59.50
        ~1989.12.31..23.59.49  ~1987.12.31..23.59.48
        ~1985.6.30..23.59.47   ~1983.6.30..23.59.46
        ~1982.6.30..23.59.45   ~1981.6.30..23.59.44
        ~1979.12.31..23.59.43  ~1978.12.31..23.59.42
        ~1977.12.31..23.59.41  ~1976.12.31..23.59.40
        ~1975.12.31..23.59.39  ~1974.12.31..23.59.38
        ~1973.12.31..23.59.37  ~1972.12.31..23.59.36
        ~1972.6.30..23.59.35
    ==
::

Produces a list of absolute dates (@da) that represent the Urbit Galactc Time equivalents of the UTC leap second dates in ++les.

~zod/try=/hom> lef:yu
~[
  ~2012.6.30..23.59.59
  ~2008.12.31..23.59.58
  ~2005.12.31..23.59.57
  ~1998.12.31..23.59.56
  ~1997.6.30..23.59.55
  ~1995.12.31..23.59.54
  ~1994.6.30..23.59.53
  ~1993.6.30..23.59.52
  ~1992.6.30..23.59.51
  ~1990.12.31..23.59.50
  ~1989.12.31..23.59.49
  ~1987.12.31..23.59.48
  ~1985.6.30..23.59.47
  ~1983.6.30..23.59.46
  ~1982.6.30..23.59.45
  ~1981.6.30..23.59.44
  ~1979.12.31..23.59.43
  ~1978.12.31..23.59.42
  ~1977.12.31..23.59.41
  ~1976.12.31..23.59.40
  ~1975.12.31..23.59.39
  ~1974.12.31..23.59.38
  ~1973.12.31..23.59.37
  ~1972.12.31..23.59.36
  ~1972.6.30..23.59.35
]
~zod/try=/hom> (snag 2 lef:yu)
~2005.12.31..23.59.57