clojure rfc3339 simple date format

thread-local-utc-date-format.clj

(def ^:private thread-local-utc-date-format
;; SimpleDateFormat is not thread-safe, so we use a ThreadLocal proxy for access.
;; http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4228335
(proxy [ThreadLocal] []
(initialValue []
(doto (java.text.SimpleDateFormat. "yyyy-MM-dd'T'HH:mm:ss.SSS-00:00")
;; RFC3339 says to use -00:00 when the timezone is unknown (+00:00 implies a known GMT)
(.setTimeZone (java.util.TimeZone/getTimeZone "GMT"))))))

(defn write-date
  "Write a java.util.Date using the IWriter protocol
as RFC3339 timestamp, always in UTC."
  [^java.util.Date d w]
  (let [utc-format (.get thread-local-utc-date-format)]
    (writer/write w "#inst \"")
    (writer/write w (.format utc-format d))
    (writer/write w "\"")))
  
  url:  https://github.com/edn-format/data.edn/blob/master/src/org/edn_format/print/util.clj