anchor.diff:  
   ====
   `+` - Add a duration to an instant:
  -
   [source.code,clojure]
   ----
   (t/+ (t/now)
        (t/new-duration 10 :minutes))
   ----
  -
  +====
  +
  +====
   `-` - Subtract a duration to an instant:
  -
   [source.code,clojure]
   ----
   (t/- (t/now)
  -     (t/new-duraion 10 :hours))
  -----
  -
  +     (t/new-duration 10 :hours))
  +----
  +====
  +
  +====
   `<<` - Go back in time a duration:
  -
   [source.code,clojure]
   ----
   (t/<< (t/now) (t/new-period 10 :weeks))
   ----
  -
  +====
  +
  +====
   `>>` - Go forward in time a duration:
  -
   [source.code,clojure]
   ----
   (t/>> (t/now) (t/new-duration 10 :hours))
   ----
  -
  +====
  +
  +====
   `<` - Before?
  -
   [source.code,clojure]
   ----
   (t/< (t/instant "2000-01-01T00:00") (t/instant "2018-01-01T00:00"))
   ----
  -
  +====
  +
  +====
   `>` - After?
  -
   [source.code,clojure]
   ----
   (t/> (t/instant "2000-01-01T00:00") (t/instant "2018-01-01T00:00"))
   ----
  -
  -`<=` - Before or same time?
  -
  +====
  +
  +====
  +`\<=` - Before or same time?
   [source.code,clojure]
   ----
   (t/<= (t/instant "2000-01-01T00:00") (t/instant "2018-01-01T00:00"))
   ----
  -
  +====
  +
  +====
   `>=` - After or same time?
  -
   [source.code,clojure]
   ----
   (t/>= (t/instant "2000-01-01T00:00") (t/instant "2018-01-01T00:00"))
   ----
  -
  +====
  +
  +====
   `ago` - Give the time a duration ago:
  -
   [source.code,clojure]
   ----
   (t/ago (t/new-duration 1 :hours))
   ----
  -
  -TBD
  -am
  -
  -[source.code,clojure]
  -----
  -
  -----
  -
  +====
  +
  +====
  +`am` - Create an interval spanning the morning of a given date:
  +[source.code,clojure]
  +----
  +(t/am (t/date "2018-01-01"))
  +----
  +====
  +
  +====
   `at` - Make date-time from a date (given date `at` "time"):
  -
   [source.code,clojure]
   ----
   (-> (t/date "2000-01-01") (t/at "00:00"))
   ----
  -
  -TBD atom?
  -
  -
  -[source.code,clojure]
  -----
  -
  -----
  -
  +====
  +
  +====
  +`atom` - TBD
  +[source.code,clojure]
  +----
  +
  +----
  +====
  +
  +====
   `beginning` - Give the beginning of an interval:
  -
   [source.code,clojure]
   ----
   (t/beginning (t/today))
   ----
  -
  +====
  +
  +====
   `between` - Give a value for the duration between two instances:
  -
   [source.code,clojure]
   ----
   (t/between (t/instant "2000-01-01T00:00") (t/instant "2018-01-01T00:00"))
   ----
  -
  +====
  +
  +====
   `bounds` - Give the beginning and end of an interval:
  -
   [source.code,clojure]
   ----
   (t/bounds (t/yesterday))
   ----
  -
  +====
  +
  +====
   `clock` - Create a system clock or fixed clock:
  -
   [source.code,clojure]
   ----
   (t/clock)
   ----
  -
   [source.code,clojure]
   ----
   (t/clock (t/instant "2018-01-01T00:00"))
   ----
  -
  -
  -TDB coincident?
  -compare-and-set!
  -compliemnt
  -concur
  -concurrencies
  -conj
  -
  -[source.code,clojure]
  -----
  -
  -----
  -
  +====
  +
  +====
  +`coincident?` - Are two intervals the same?
  +[source.code,clojure]
  +----
  +(t/coincident? (t/today) (t/today))
  +----
  +====
  +
  +====
  +`compare-and-set!` - TBD (Atomic clocks)
  +[source.code,clojure]
  +----
  +
  +----
  +====
  +
  +====
  +`complement` - Give the inverse intervals. - TBD : better description.
  +[source.code,clojure]
  +----
  +(t/complement [(t/instant "2010-01-01T00:00")
  +	       (t/instant "2010-02-01T00:00")
  +	       (t/instant "2010-03-01T00:00")])
  +----
  +====
  +
  +====
  +`concur` - Get the common interval (if any) of two intervals.
  +[source.code,clojure]
  +----
  +(t/concur (t/today) (t/new-interval (t/yesterday) (t/tomorrow)))
  +----
  +====
  +
  +====
  +`concurrencies` - A sequence of times when intervals overlap: - TBD Better definition.
  +[source.code,clojure]
  +----
  +(t/concurrencies (t/today) (t/new-interval (t/today) (t/tomorrow)))
  +----
  +====
  +
  +====
  +`conj` - TBD
  +[source.code,clojure]
  +----
  +
  +----
  +====
  +
  +====
   `date` - Get the date:
  -
   [source.code,clojure]
   ----
   (t/date)
  
positive.code: ----
  (t/month "2018-11-11")
  ----
  
  `months` - Get the number of months in a duration:
  
  [source.code,clojure]
  ----
  (t/months (t/new-period 10 :months))
  ----
  
  `nanos` - Get the number of nanoseconds in a duration:
  
  [source.code,clojure]
  ----
  (t/nanos (t/new-duration 5 :minutes))
  ----
  
  `nanosecond` - Get the nanosecond of the time:
  
  [source.code,clojure]
  ----
  (t/nanosecond (t/now))
  ----
  
  `new-date` - Created a new `java.time.LocalDate`
  
  [source.code,clojure]
  
negative.code: ----
  (t/date "2018-01-01T00:00")
  ----
  ====
  
  ====
  `day-of-month` - Get the numerical day of the month:
  [source.code,clojure]
  ----
  (t/day-of-month)
  